diff --git a/test/Microsoft.AspNetCore.Mvc.Abstractions.Test/ModelBinding/ModelStateDictionaryTest.cs b/test/Microsoft.AspNetCore.Mvc.Abstractions.Test/ModelBinding/ModelStateDictionaryTest.cs
index 90abb75dd2..36a7f874c8 100644
--- a/test/Microsoft.AspNetCore.Mvc.Abstractions.Test/ModelBinding/ModelStateDictionaryTest.cs
+++ b/test/Microsoft.AspNetCore.Mvc.Abstractions.Test/ModelBinding/ModelStateDictionaryTest.cs
@@ -119,7 +119,7 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
             dictionary.Clear();
 
             // Assert
-            Assert.Equal(0, dictionary.Count);
+            Assert.Empty(dictionary);
             Assert.Equal(0, dictionary.ErrorCount);
             Assert.Empty(dictionary);
             Assert.Equal(ModelValidationState.Valid, dictionary.ValidationState);
@@ -135,7 +135,7 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
             dictionary.Clear();
 
             // Assert
-            Assert.Equal(0, dictionary.Count);
+            Assert.Empty(dictionary);
             Assert.Equal(0, dictionary.ErrorCount);
             Assert.Empty(dictionary);
             Assert.Equal(ModelValidationState.Valid, dictionary.ValidationState);
@@ -180,7 +180,7 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
 
             // Assert
             Assert.Equal(0, source.ErrorCount);
-            Assert.Equal(1, source.Count);
+            Assert.Single(source);
             Assert.Equal(ModelValidationState.Skipped, source["key"].ValidationState);
         }
 
@@ -239,7 +239,7 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
 
             // Assert
             Assert.Equal(0, source.ErrorCount);
-            Assert.Equal(1, source.Count);
+            Assert.Single(source);
             Assert.Equal(ModelValidationState.Valid, source["key"].ValidationState);
         }
 
@@ -276,7 +276,7 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding
 
             // Assert
             Assert.Equal(2, target.ErrorCount);
-            Assert.Equal(1, target.Count);
+            Assert.Single(target);
             var actual = target["key"];
             Assert.Equal(entry.RawValue, actual.RawValue);
             Assert.Equal(entry.AttemptedValue, actual.AttemptedValue);
diff --git a/test/Microsoft.AspNetCore.Mvc.Core.Test/ControllerBaseTest.cs b/test/Microsoft.AspNetCore.Mvc.Core.Test/ControllerBaseTest.cs
index 19664bba03..f3626af235 100644
--- a/test/Microsoft.AspNetCore.Mvc.Core.Test/ControllerBaseTest.cs
+++ b/test/Microsoft.AspNetCore.Mvc.Core.Test/ControllerBaseTest.cs
@@ -2751,7 +2751,7 @@ namespace Microsoft.AspNetCore.Mvc.Core.Test
 
             // Assert
             Assert.False(result);
-            Assert.Equal(1, controller.ModelState.Count);
+            Assert.Single(controller.ModelState);
             var error = Assert.Single(controller.ModelState["Prefix.IntegerProperty"].Errors);
             Assert.Equal("Out of range!", error.ErrorMessage);
         }
@@ -2787,7 +2787,7 @@ namespace Microsoft.AspNetCore.Mvc.Core.Test
 
             // Assert
             Assert.False(result);
-            Assert.Equal(1, controller.ModelState.Count);
+            Assert.Single(controller.ModelState);
             var error = Assert.Single(controller.ModelState["IntegerProperty"].Errors);
             Assert.Equal("Out of range!", error.ErrorMessage);
         }
diff --git a/test/Microsoft.AspNetCore.Mvc.Core.Test/Internal/DefaultObjectValidatorTests.cs b/test/Microsoft.AspNetCore.Mvc.Core.Test/Internal/DefaultObjectValidatorTests.cs
index e6caec6464..883a485de2 100644
--- a/test/Microsoft.AspNetCore.Mvc.Core.Test/Internal/DefaultObjectValidatorTests.cs
+++ b/test/Microsoft.AspNetCore.Mvc.Core.Test/Internal/DefaultObjectValidatorTests.cs
@@ -614,7 +614,7 @@ namespace Microsoft.AspNetCore.Mvc.Internal
 
             // Assert
             Assert.True(modelState.IsValid);
-            Assert.Equal(1, modelState.Count);
+            Assert.Single(modelState);
 
             var entry = modelState["parameter"];
             Assert.Equal(ModelValidationState.Valid, entry.ValidationState);
diff --git a/test/Microsoft.AspNetCore.Mvc.Core.Test/ModelBinding/Binders/ComplexTypeModelBinderTest.cs b/test/Microsoft.AspNetCore.Mvc.Core.Test/ModelBinding/Binders/ComplexTypeModelBinderTest.cs
index 43300f7dbf..c188a909ef 100644
--- a/test/Microsoft.AspNetCore.Mvc.Core.Test/ModelBinding/Binders/ComplexTypeModelBinderTest.cs
+++ b/test/Microsoft.AspNetCore.Mvc.Core.Test/ModelBinding/Binders/ComplexTypeModelBinderTest.cs
@@ -664,7 +664,7 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding.Binders
             // Assert
             var modelStateDictionary = bindingContext.ModelState;
             Assert.False(modelStateDictionary.IsValid);
-            Assert.Equal(1, modelStateDictionary.Count);
+            Assert.Single(modelStateDictionary);
 
             // Check Age error.
             ModelStateEntry entry;
diff --git a/test/Microsoft.AspNetCore.Mvc.IntegrationTests/BodyValidationIntegrationTests.cs b/test/Microsoft.AspNetCore.Mvc.IntegrationTests/BodyValidationIntegrationTests.cs
index 27e48d1500..33b287aa97 100644
--- a/test/Microsoft.AspNetCore.Mvc.IntegrationTests/BodyValidationIntegrationTests.cs
+++ b/test/Microsoft.AspNetCore.Mvc.IntegrationTests/BodyValidationIntegrationTests.cs
@@ -578,7 +578,7 @@ namespace Microsoft.AspNetCore.Mvc.IntegrationTests
             Assert.Null(boundPerson.Address);
 
             Assert.False(modelState.IsValid);
-            Assert.Equal(1, modelState.Count);
+            Assert.Single(modelState);
             Assert.Equal(1, modelState.ErrorCount);
 
             var state = modelState["CustomParameter.Address.Number"];
diff --git a/test/Microsoft.AspNetCore.Mvc.IntegrationTests/CancellationTokenModelBinderIntegrationTest.cs b/test/Microsoft.AspNetCore.Mvc.IntegrationTests/CancellationTokenModelBinderIntegrationTest.cs
index 26552ccfce..9ce033b2a8 100644
--- a/test/Microsoft.AspNetCore.Mvc.IntegrationTests/CancellationTokenModelBinderIntegrationTest.cs
+++ b/test/Microsoft.AspNetCore.Mvc.IntegrationTests/CancellationTokenModelBinderIntegrationTest.cs
@@ -92,7 +92,7 @@ namespace Microsoft.AspNetCore.Mvc.IntegrationTests
 
             // ModelState
             Assert.True(modelState.IsValid);
-            Assert.Equal(0, modelState.Count);
+            Assert.Empty(modelState);
         }
 
         [Fact]
@@ -130,7 +130,7 @@ namespace Microsoft.AspNetCore.Mvc.IntegrationTests
 
             // ModelState
             Assert.True(modelState.IsValid);
-            Assert.Equal(0, modelState.Count);
+            Assert.Empty(modelState);
         }
     }
 }
\ No newline at end of file
diff --git a/test/Microsoft.AspNetCore.Mvc.IntegrationTests/ComplexTypeModelBinderIntegrationTest.cs b/test/Microsoft.AspNetCore.Mvc.IntegrationTests/ComplexTypeModelBinderIntegrationTest.cs
index abd9e23933..49f64eacfa 100644
--- a/test/Microsoft.AspNetCore.Mvc.IntegrationTests/ComplexTypeModelBinderIntegrationTest.cs
+++ b/test/Microsoft.AspNetCore.Mvc.IntegrationTests/ComplexTypeModelBinderIntegrationTest.cs
@@ -80,7 +80,7 @@ namespace Microsoft.AspNetCore.Mvc.IntegrationTests
             Assert.NotNull(model.Customer.Address);
             Assert.Equal(AddressStreetContent, model.Customer.Address.Street);
 
-            Assert.Equal(1, modelState.Count);
+            Assert.Single(modelState);
             Assert.Equal(0, modelState.ErrorCount);
             Assert.True(modelState.IsValid);
 
@@ -122,7 +122,7 @@ namespace Microsoft.AspNetCore.Mvc.IntegrationTests
             Assert.NotNull(model.Customer.Address);
             Assert.Equal(AddressStreetContent, model.Customer.Address.Street);
 
-            Assert.Equal(1, modelState.Count);
+            Assert.Single(modelState);
             Assert.Equal(0, modelState.ErrorCount);
             Assert.True(modelState.IsValid);
 
@@ -167,7 +167,7 @@ namespace Microsoft.AspNetCore.Mvc.IntegrationTests
             Assert.Equal("bill", model.Customer.Name);
             Assert.Null(model.Customer.Address);
 
-            Assert.Equal(1, modelState.Count);
+            Assert.Single(modelState);
             Assert.Equal(0, modelState.ErrorCount);
             Assert.True(modelState.IsValid);
 
@@ -209,7 +209,7 @@ namespace Microsoft.AspNetCore.Mvc.IntegrationTests
             Assert.Null(model.Customer);
             Assert.Equal(10, model.ProductId);
 
-            Assert.Equal(1, modelState.Count);
+            Assert.Single(modelState);
             Assert.Equal(0, modelState.ErrorCount);
             Assert.True(modelState.IsValid);
 
@@ -250,7 +250,7 @@ namespace Microsoft.AspNetCore.Mvc.IntegrationTests
             var model = Assert.IsType<Order1>(modelBindingResult.Model);
             Assert.Null(model.Customer);
 
-            Assert.Equal(0, modelState.Count);
+            Assert.Empty(modelState);
             Assert.Equal(0, modelState.ErrorCount);
             Assert.True(modelState.IsValid);
         }
@@ -389,7 +389,7 @@ namespace Microsoft.AspNetCore.Mvc.IntegrationTests
             Assert.Equal("bill", model.Customer.Name);
             Assert.Null(model.Customer.Token);
 
-            Assert.Equal(1, modelState.Count);
+            Assert.Single(modelState);
             Assert.Equal(0, modelState.ErrorCount);
             Assert.True(modelState.IsValid);
 
@@ -578,7 +578,7 @@ namespace Microsoft.AspNetCore.Mvc.IntegrationTests
             Assert.Null(model.Customer);
             Assert.Equal(10, model.ProductId);
 
-            Assert.Equal(1, modelState.Count);
+            Assert.Single(modelState);
             Assert.Equal(0, modelState.ErrorCount);
             Assert.True(modelState.IsValid);
 
@@ -619,7 +619,7 @@ namespace Microsoft.AspNetCore.Mvc.IntegrationTests
             var model = Assert.IsType<Order4>(modelBindingResult.Model);
             Assert.Null(model.Customer);
 
-            Assert.Equal(0, modelState.Count);
+            Assert.Empty(modelState);
             Assert.Equal(0, modelState.ErrorCount);
             Assert.True(modelState.IsValid);
         }
@@ -756,7 +756,7 @@ namespace Microsoft.AspNetCore.Mvc.IntegrationTests
             Assert.Equal("bill", model.Name);
             Assert.Null(model.ProductIds);
 
-            Assert.Equal(1, modelState.Count);
+            Assert.Single(modelState);
             Assert.Equal(0, modelState.ErrorCount);
             Assert.True(modelState.IsValid);
 
@@ -795,7 +795,7 @@ namespace Microsoft.AspNetCore.Mvc.IntegrationTests
             Assert.Null(model.Name);
             Assert.Null(model.ProductIds);
 
-            Assert.Equal(0, modelState.Count);
+            Assert.Empty(modelState);
             Assert.Equal(0, modelState.ErrorCount);
             Assert.True(modelState.IsValid);
         }
@@ -932,7 +932,7 @@ namespace Microsoft.AspNetCore.Mvc.IntegrationTests
             Assert.Equal("bill", model.Name);
             Assert.Null(model.ProductIds);
 
-            Assert.Equal(1, modelState.Count);
+            Assert.Single(modelState);
             Assert.Equal(0, modelState.ErrorCount);
             Assert.True(modelState.IsValid);
 
@@ -971,7 +971,7 @@ namespace Microsoft.AspNetCore.Mvc.IntegrationTests
             Assert.Null(model.Name);
             Assert.Null(model.ProductIds);
 
-            Assert.Equal(0, modelState.Count);
+            Assert.Empty(modelState);
             Assert.Equal(0, modelState.ErrorCount);
             Assert.True(modelState.IsValid);
         }
@@ -1108,7 +1108,7 @@ namespace Microsoft.AspNetCore.Mvc.IntegrationTests
             Assert.Equal("bill", model.Name);
             Assert.Null(model.ProductIds);
 
-            Assert.Equal(1, modelState.Count);
+            Assert.Single(modelState);
             Assert.Equal(0, modelState.ErrorCount);
             Assert.True(modelState.IsValid);
 
@@ -1147,7 +1147,7 @@ namespace Microsoft.AspNetCore.Mvc.IntegrationTests
             Assert.Null(model.Name);
             Assert.Null(model.ProductIds);
 
-            Assert.Equal(0, modelState.Count);
+            Assert.Empty(modelState);
             Assert.Equal(0, modelState.ErrorCount);
             Assert.True(modelState.IsValid);
         }
@@ -1609,7 +1609,7 @@ namespace Microsoft.AspNetCore.Mvc.IntegrationTests
             Assert.Equal("bill", model.Name);
             Assert.Equal(default(KeyValuePair<string, int>), model.ProductId);
 
-            Assert.Equal(1, modelState.Count);
+            Assert.Single(modelState);
             Assert.Equal(0, modelState.ErrorCount);
             Assert.True(modelState.IsValid);
 
@@ -1648,7 +1648,7 @@ namespace Microsoft.AspNetCore.Mvc.IntegrationTests
             Assert.Null(model.Name);
             Assert.Equal(default(KeyValuePair<string, int>), model.ProductId);
 
-            Assert.Equal(0, modelState.Count);
+            Assert.Empty(modelState);
             Assert.Equal(0, modelState.ErrorCount);
             Assert.True(modelState.IsValid);
         }
@@ -1784,7 +1784,7 @@ namespace Microsoft.AspNetCore.Mvc.IntegrationTests
             Assert.NotNull(model.Customer.Address);
             Assert.Equal(AddressStreetContent, model.Customer.Address.Street);
 
-            Assert.Equal(0, modelState.Count);
+            Assert.Empty(modelState);
             Assert.Equal(0, modelState.ErrorCount);
             Assert.True(modelState.IsValid);
         }
@@ -1826,7 +1826,7 @@ namespace Microsoft.AspNetCore.Mvc.IntegrationTests
             var model = Assert.IsType<Order10>(modelBindingResult.Model);
             Assert.Null(model.Customer);
 
-            Assert.Equal(1, modelState.Count);
+            Assert.Single(modelState);
             Assert.Equal(1, modelState.ErrorCount);
             Assert.False(modelState.IsValid);
 
@@ -1873,7 +1873,7 @@ namespace Microsoft.AspNetCore.Mvc.IntegrationTests
             var model = Assert.IsType<Order10>(modelBindingResult.Model);
             Assert.Null(model.Customer);
 
-            Assert.Equal(1, modelState.Count);
+            Assert.Single(modelState);
             Assert.Equal(1, modelState.ErrorCount);
             Assert.False(modelState.IsValid);
 
@@ -2074,7 +2074,7 @@ namespace Microsoft.AspNetCore.Mvc.IntegrationTests
             var model = Assert.IsType<Order12>(modelBindingResult.Model);
             Assert.Null(model.ProductName);
 
-            Assert.Equal(1, modelState.Count);
+            Assert.Single(modelState);
             Assert.Equal(1, modelState.ErrorCount);
             Assert.False(modelState.IsValid);
 
@@ -2118,7 +2118,7 @@ namespace Microsoft.AspNetCore.Mvc.IntegrationTests
             var model = Assert.IsType<Order12>(modelBindingResult.Model);
             Assert.Null(model.ProductName);
 
-            Assert.Equal(1, modelState.Count);
+            Assert.Single(modelState);
             Assert.Equal(1, modelState.ErrorCount);
             Assert.False(modelState.IsValid);
 
@@ -2158,7 +2158,7 @@ namespace Microsoft.AspNetCore.Mvc.IntegrationTests
             var model = Assert.IsType<Order12>(modelBindingResult.Model);
             Assert.Equal("abc", model.ProductName);
 
-            Assert.Equal(1, modelState.Count);
+            Assert.Single(modelState);
             Assert.Equal(0, modelState.ErrorCount);
             Assert.True(modelState.IsValid);
 
@@ -2202,7 +2202,7 @@ namespace Microsoft.AspNetCore.Mvc.IntegrationTests
             var model = Assert.IsType<Order13>(modelBindingResult.Model);
             Assert.Null(model.OrderIds);
 
-            Assert.Equal(1, modelState.Count);
+            Assert.Single(modelState);
             Assert.Equal(1, modelState.ErrorCount);
             Assert.False(modelState.IsValid);
 
@@ -2246,7 +2246,7 @@ namespace Microsoft.AspNetCore.Mvc.IntegrationTests
             var model = Assert.IsType<Order13>(modelBindingResult.Model);
             Assert.Null(model.OrderIds);
 
-            Assert.Equal(1, modelState.Count);
+            Assert.Single(modelState);
             Assert.Equal(1, modelState.ErrorCount);
             Assert.False(modelState.IsValid);
 
@@ -2286,7 +2286,7 @@ namespace Microsoft.AspNetCore.Mvc.IntegrationTests
             var model = Assert.IsType<Order13>(modelBindingResult.Model);
             Assert.Equal(new[] { 123 }, model.OrderIds.ToArray());
 
-            Assert.Equal(1, modelState.Count);
+            Assert.Single(modelState);
             Assert.Equal(0, modelState.ErrorCount);
             Assert.True(modelState.IsValid);
 
@@ -2332,7 +2332,7 @@ namespace Microsoft.AspNetCore.Mvc.IntegrationTests
             Assert.NotNull(model);
             Assert.Equal(0, model.ProductId);
 
-            Assert.Equal(1, modelState.Count);
+            Assert.Single(modelState);
             Assert.Equal(1, modelState.ErrorCount);
             Assert.False(modelState.IsValid);
 
diff --git a/test/Microsoft.AspNetCore.Mvc.IntegrationTests/GenericModelBinderIntegrationTest.cs b/test/Microsoft.AspNetCore.Mvc.IntegrationTests/GenericModelBinderIntegrationTest.cs
index bf10111e82..acb91f6ed5 100644
--- a/test/Microsoft.AspNetCore.Mvc.IntegrationTests/GenericModelBinderIntegrationTest.cs
+++ b/test/Microsoft.AspNetCore.Mvc.IntegrationTests/GenericModelBinderIntegrationTest.cs
@@ -219,7 +219,7 @@ namespace Microsoft.AspNetCore.Mvc.IntegrationTests
             Assert.Single(model);
             Assert.NotNull(model[0]);
 
-            Assert.Equal(0, modelState.Count);
+            Assert.Empty(modelState);
             Assert.Equal(0, modelState.ErrorCount);
             Assert.True(modelState.IsValid);
         }
@@ -253,7 +253,7 @@ namespace Microsoft.AspNetCore.Mvc.IntegrationTests
             Assert.Single(model);
             Assert.Null(model[0]);
 
-            Assert.Equal(0, modelState.Count);
+            Assert.Empty(modelState);
             Assert.Equal(0, modelState.ErrorCount);
             Assert.True(modelState.IsValid);
         }
@@ -378,7 +378,7 @@ namespace Microsoft.AspNetCore.Mvc.IntegrationTests
             Assert.NotNull(model);
             Assert.Empty(model);
 
-            Assert.Equal(0, modelState.Count);
+            Assert.Empty(modelState);
             Assert.Equal(0, modelState.ErrorCount);
             Assert.True(modelState.IsValid);
         }
@@ -501,7 +501,7 @@ namespace Microsoft.AspNetCore.Mvc.IntegrationTests
             Assert.NotNull(model);
             Assert.Empty(model);
 
-            Assert.Equal(0, modelState.Count);
+            Assert.Empty(modelState);
             Assert.Equal(0, modelState.ErrorCount);
             Assert.True(modelState.IsValid);
         }
@@ -633,7 +633,7 @@ namespace Microsoft.AspNetCore.Mvc.IntegrationTests
             Assert.NotNull(model);
             Assert.Empty(model);
 
-            Assert.Equal(0, modelState.Count);
+            Assert.Empty(modelState);
             Assert.Equal(0, modelState.ErrorCount);
             Assert.True(modelState.IsValid);
         }
diff --git a/test/Microsoft.AspNetCore.Mvc.IntegrationTests/KeyValuePairModelBinderIntegrationTest.cs b/test/Microsoft.AspNetCore.Mvc.IntegrationTests/KeyValuePairModelBinderIntegrationTest.cs
index 985fe67c2c..79c0803f15 100644
--- a/test/Microsoft.AspNetCore.Mvc.IntegrationTests/KeyValuePairModelBinderIntegrationTest.cs
+++ b/test/Microsoft.AspNetCore.Mvc.IntegrationTests/KeyValuePairModelBinderIntegrationTest.cs
@@ -332,7 +332,7 @@ namespace Microsoft.AspNetCore.Mvc.IntegrationTests
 
             Assert.Equal(new KeyValuePair<string, int>(), modelBindingResult.Model);
 
-            Assert.Equal(0, modelState.Count);
+            Assert.Empty(modelState);
             Assert.Equal(0, modelState.ErrorCount);
             Assert.True(modelState.IsValid);
         }
@@ -495,7 +495,7 @@ namespace Microsoft.AspNetCore.Mvc.IntegrationTests
 
             Assert.Equal(new KeyValuePair<string, Person>(), modelBindingResult.Model);
 
-            Assert.Equal(0, modelState.Count);
+            Assert.Empty(modelState);
             Assert.Equal(0, modelState.ErrorCount);
             Assert.True(modelState.IsValid);
         }
diff --git a/test/Microsoft.AspNetCore.Mvc.IntegrationTests/ModelPrefixSelectionIntegrationTest.cs b/test/Microsoft.AspNetCore.Mvc.IntegrationTests/ModelPrefixSelectionIntegrationTest.cs
index 34de696859..7a03494307 100644
--- a/test/Microsoft.AspNetCore.Mvc.IntegrationTests/ModelPrefixSelectionIntegrationTest.cs
+++ b/test/Microsoft.AspNetCore.Mvc.IntegrationTests/ModelPrefixSelectionIntegrationTest.cs
@@ -55,7 +55,7 @@ namespace Microsoft.AspNetCore.Mvc.IntegrationTests
             var model = Assert.IsType<Person1>(modelBindingResult.Model);
             Assert.Null(model.Name);
 
-            Assert.Equal(0, modelState.Count);
+            Assert.Empty(modelState);
             Assert.Equal(0, modelState.ErrorCount);
             Assert.True(modelState.IsValid);
         }
@@ -104,7 +104,7 @@ namespace Microsoft.AspNetCore.Mvc.IntegrationTests
             var model = Assert.IsType<Person2>(modelBindingResult.Model);
             Assert.Null(model.Name);
 
-            Assert.Equal(0, modelState.Count);
+            Assert.Empty(modelState);
             Assert.Equal(0, modelState.ErrorCount);
             Assert.True(modelState.IsValid);
         }
@@ -143,7 +143,7 @@ namespace Microsoft.AspNetCore.Mvc.IntegrationTests
             var model = Assert.IsType<Person3>(modelBindingResult.Model);
             Assert.Null(model.Name);
 
-            Assert.Equal(0, modelState.Count);
+            Assert.Empty(modelState);
             Assert.Equal(0, modelState.ErrorCount);
             Assert.True(modelState.IsValid);
         }
@@ -192,7 +192,7 @@ namespace Microsoft.AspNetCore.Mvc.IntegrationTests
             var model = Assert.IsType<Person4>(modelBindingResult.Model);
             Assert.Null(model.Name);
 
-            Assert.Equal(0, modelState.Count);
+            Assert.Empty(modelState);
             Assert.Equal(0, modelState.ErrorCount);
             Assert.True(modelState.IsValid);
         }
@@ -238,7 +238,7 @@ namespace Microsoft.AspNetCore.Mvc.IntegrationTests
             var model = Assert.IsType<Person5>(modelBindingResult.Model);
             Assert.Null(model.Name);
 
-            Assert.Equal(0, modelState.Count);
+            Assert.Empty(modelState);
             Assert.Equal(0, modelState.ErrorCount);
             Assert.True(modelState.IsValid);
         }
diff --git a/test/Microsoft.AspNetCore.Mvc.IntegrationTests/SimpleTypeModelBinderIntegrationTest.cs b/test/Microsoft.AspNetCore.Mvc.IntegrationTests/SimpleTypeModelBinderIntegrationTest.cs
index daddf74bda..0d5cede662 100644
--- a/test/Microsoft.AspNetCore.Mvc.IntegrationTests/SimpleTypeModelBinderIntegrationTest.cs
+++ b/test/Microsoft.AspNetCore.Mvc.IntegrationTests/SimpleTypeModelBinderIntegrationTest.cs
@@ -274,7 +274,7 @@ namespace Microsoft.AspNetCore.Mvc.IntegrationTests
 
             // ModelState
             Assert.False(modelState.IsValid);
-            Assert.Equal(1, modelState.Count);
+            Assert.Single(modelState);
             Assert.Equal(1, modelState.ErrorCount);
 
             var key = Assert.Single(modelState.Keys);
@@ -332,7 +332,7 @@ namespace Microsoft.AspNetCore.Mvc.IntegrationTests
 
             // ModelState
             Assert.False(modelState.IsValid);
-            Assert.Equal(1, modelState.Count);
+            Assert.Single(modelState);
             Assert.Equal(1, modelState.ErrorCount);
 
             var key = Assert.Single(modelState.Keys);
diff --git a/test/Microsoft.AspNetCore.Mvc.IntegrationTests/ValidationIntegrationTests.cs b/test/Microsoft.AspNetCore.Mvc.IntegrationTests/ValidationIntegrationTests.cs
index a0cc60067d..036f758433 100644
--- a/test/Microsoft.AspNetCore.Mvc.IntegrationTests/ValidationIntegrationTests.cs
+++ b/test/Microsoft.AspNetCore.Mvc.IntegrationTests/ValidationIntegrationTests.cs
@@ -187,7 +187,7 @@ namespace Microsoft.AspNetCore.Mvc.IntegrationTests
             var model = Assert.IsType<Order1>(modelBindingResult.Model);
             Assert.Equal("bill", model.CustomerName);
 
-            Assert.Equal(1, modelState.Count);
+            Assert.Single(modelState);
             Assert.Equal(0, modelState.ErrorCount);
             Assert.True(modelState.IsValid);
 
@@ -224,7 +224,7 @@ namespace Microsoft.AspNetCore.Mvc.IntegrationTests
             var model = Assert.IsType<Order1>(modelBindingResult.Model);
             Assert.Null(model.CustomerName);
 
-            Assert.Equal(1, modelState.Count);
+            Assert.Single(modelState);
             Assert.Equal(1, modelState.ErrorCount);
             Assert.False(modelState.IsValid);
 
@@ -276,7 +276,7 @@ namespace Microsoft.AspNetCore.Mvc.IntegrationTests
             Assert.NotNull(model.Customer);
             Assert.Equal("bill", model.Customer.Name);
 
-            Assert.Equal(1, modelState.Count);
+            Assert.Single(modelState);
             Assert.Equal(0, modelState.ErrorCount);
             Assert.True(modelState.IsValid);
 
@@ -313,7 +313,7 @@ namespace Microsoft.AspNetCore.Mvc.IntegrationTests
             var model = Assert.IsType<Order2>(modelBindingResult.Model);
             Assert.Null(model.Customer);
 
-            Assert.Equal(1, modelState.Count);
+            Assert.Single(modelState);
             Assert.Equal(1, modelState.ErrorCount);
             Assert.False(modelState.IsValid);
 
@@ -367,7 +367,7 @@ namespace Microsoft.AspNetCore.Mvc.IntegrationTests
             Assert.NotNull(model.Customer);
             Assert.Equal("bill", model.Customer.Name);
 
-            Assert.Equal(1, modelState.Count);
+            Assert.Single(modelState);
             Assert.Equal(0, modelState.ErrorCount);
             Assert.True(modelState.IsValid);
 
@@ -459,7 +459,7 @@ namespace Microsoft.AspNetCore.Mvc.IntegrationTests
             Assert.NotNull(model.Items);
             Assert.Equal(17, Assert.Single(model.Items).ItemId);
 
-            Assert.Equal(1, modelState.Count);
+            Assert.Single(modelState);
             Assert.Equal(0, modelState.ErrorCount);
             Assert.True(modelState.IsValid);
 
@@ -497,7 +497,7 @@ namespace Microsoft.AspNetCore.Mvc.IntegrationTests
             var model = Assert.IsType<Order4>(modelBindingResult.Model);
             Assert.Null(model.Items);
 
-            Assert.Equal(1, modelState.Count);
+            Assert.Single(modelState);
             Assert.Equal(1, modelState.ErrorCount);
             Assert.False(modelState.IsValid);
 
@@ -545,7 +545,7 @@ namespace Microsoft.AspNetCore.Mvc.IntegrationTests
             var model = Assert.IsType<List<Order5>>(modelBindingResult.Model);
             Assert.Equal(17, Assert.Single(model).ProductId);
 
-            Assert.Equal(1, modelState.Count);
+            Assert.Single(modelState);
             Assert.Equal(0, modelState.ErrorCount);
             Assert.True(modelState.IsValid);
 
@@ -631,7 +631,7 @@ namespace Microsoft.AspNetCore.Mvc.IntegrationTests
             var model = Assert.IsType<Order6>(modelBindingResult.Model);
             Assert.Equal("bill", model.Name);
 
-            Assert.Equal(1, modelState.Count);
+            Assert.Single(modelState);
             Assert.Equal(0, modelState.ErrorCount);
             Assert.True(modelState.IsValid);
 
@@ -668,7 +668,7 @@ namespace Microsoft.AspNetCore.Mvc.IntegrationTests
             var model = Assert.IsType<Order6>(modelBindingResult.Model);
             Assert.Equal("billybob", model.Name);
 
-            Assert.Equal(1, modelState.Count);
+            Assert.Single(modelState);
             Assert.Equal(1, modelState.ErrorCount);
             Assert.False(modelState.IsValid);
 
@@ -719,7 +719,7 @@ namespace Microsoft.AspNetCore.Mvc.IntegrationTests
             var model = Assert.IsType<Order7>(modelBindingResult.Model);
             Assert.Equal("bill", model.Customer.Name);
 
-            Assert.Equal(1, modelState.Count);
+            Assert.Single(modelState);
             Assert.Equal(0, modelState.ErrorCount);
             Assert.True(modelState.IsValid);
 
@@ -756,7 +756,7 @@ namespace Microsoft.AspNetCore.Mvc.IntegrationTests
             var model = Assert.IsType<Order7>(modelBindingResult.Model);
             Assert.Equal("billybob", model.Customer.Name);
 
-            Assert.Equal(1, modelState.Count);
+            Assert.Single(modelState);
             Assert.Equal(1, modelState.ErrorCount);
             Assert.False(modelState.IsValid);
 
@@ -796,7 +796,7 @@ namespace Microsoft.AspNetCore.Mvc.IntegrationTests
             var model = Assert.IsType<Order7>(modelBindingResult.Model);
             Assert.Null(model.Customer);
 
-            Assert.Equal(0, modelState.Count);
+            Assert.Empty(modelState);
             Assert.Equal(0, modelState.ErrorCount);
             Assert.True(modelState.IsValid);
         }
@@ -854,7 +854,7 @@ namespace Microsoft.AspNetCore.Mvc.IntegrationTests
             var model = Assert.IsType<Order8>(modelBindingResult.Model);
             Assert.Equal("bill", model.Customer.Name);
 
-            Assert.Equal(1, modelState.Count);
+            Assert.Single(modelState);
             Assert.Equal(0, modelState.ErrorCount);
             Assert.True(modelState.IsValid);
 
@@ -961,7 +961,7 @@ namespace Microsoft.AspNetCore.Mvc.IntegrationTests
             var model = Assert.IsType<Order9>(modelBindingResult.Model);
             Assert.Equal("bill", Assert.Single(model.Products).Name);
 
-            Assert.Equal(1, modelState.Count);
+            Assert.Single(modelState);
             Assert.Equal(0, modelState.ErrorCount);
             Assert.True(modelState.IsValid);
 
@@ -1049,7 +1049,7 @@ namespace Microsoft.AspNetCore.Mvc.IntegrationTests
             var model = Assert.IsType<List<Order10>>(modelBindingResult.Model);
             Assert.Equal("bill", Assert.Single(model).Name);
 
-            Assert.Equal(1, modelState.Count);
+            Assert.Single(modelState);
             Assert.Equal(0, modelState.ErrorCount);
             Assert.True(modelState.IsValid);
 
@@ -1086,7 +1086,7 @@ namespace Microsoft.AspNetCore.Mvc.IntegrationTests
             var model = Assert.IsType<List<Order10>>(modelBindingResult.Model);
             Assert.Equal("billybob", Assert.Single(model).Name);
 
-            Assert.Equal(1, modelState.Count);
+            Assert.Single(modelState);
             Assert.Equal(1, modelState.ErrorCount);
             Assert.False(modelState.IsValid);
 
@@ -1126,7 +1126,7 @@ namespace Microsoft.AspNetCore.Mvc.IntegrationTests
             var model = Assert.IsType<List<Order10>>(modelBindingResult.Model);
             Assert.Empty(model);
 
-            Assert.Equal(0, modelState.Count);
+            Assert.Empty(modelState);
             Assert.Equal(0, modelState.ErrorCount);
             Assert.True(modelState.IsValid);
         }
@@ -1690,7 +1690,7 @@ namespace Microsoft.AspNetCore.Mvc.IntegrationTests
             Assert.Equal("Hello", message);
 
             Assert.True(modelState.IsValid);
-            Assert.Equal(1, modelState.Count);
+            Assert.Single(modelState);
 
             var entry = Assert.Single(modelState, kvp => kvp.Key == "CustomParameter.message");
             Assert.Equal(ModelValidationState.Skipped, entry.Value.ValidationState);
@@ -1732,7 +1732,7 @@ namespace Microsoft.AspNetCore.Mvc.IntegrationTests
             Assert.IsType<CancellationToken>(modelBindingResult.Model);
 
             Assert.False(modelState.IsValid);
-            Assert.Equal(1, modelState.Count);
+            Assert.Single(modelState);
 
             var entry = Assert.Single(modelState, kvp => kvp.Key == "message");
             Assert.Equal(ModelValidationState.Unvalidated, entry.Value.ValidationState);
@@ -1778,7 +1778,7 @@ namespace Microsoft.AspNetCore.Mvc.IntegrationTests
             Assert.Equal("Hello", message);
 
             Assert.False(modelState.IsValid);
-            Assert.Equal(1, modelState.Count);
+            Assert.Single(modelState);
 
             var entry = Assert.Single(modelState, kvp => kvp.Key == "other.key");
             Assert.Equal(ModelValidationState.Unvalidated, entry.Value.ValidationState);
diff --git a/test/Microsoft.AspNetCore.Mvc.ViewFeatures.Test/ViewFeatures/AttributeDictionaryTest.cs b/test/Microsoft.AspNetCore.Mvc.ViewFeatures.Test/ViewFeatures/AttributeDictionaryTest.cs
index d29e636726..93ae890858 100644
--- a/test/Microsoft.AspNetCore.Mvc.ViewFeatures.Test/ViewFeatures/AttributeDictionaryTest.cs
+++ b/test/Microsoft.AspNetCore.Mvc.ViewFeatures.Test/ViewFeatures/AttributeDictionaryTest.cs
@@ -79,7 +79,7 @@ namespace Microsoft.AspNetCore.Mvc.ViewFeatures
             attributes.Clear();
 
             // Assert
-            Assert.Equal(0, attributes.Count);
+            Assert.Empty(attributes);
             Assert.Empty(attributes);
         }
 
diff --git a/test/Microsoft.AspNetCore.Mvc.ViewFeatures.Test/ViewFeatures/ViewDataDictionaryOfTModelTest.cs b/test/Microsoft.AspNetCore.Mvc.ViewFeatures.Test/ViewFeatures/ViewDataDictionaryOfTModelTest.cs
index c656351cd5..31f0d036d6 100644
--- a/test/Microsoft.AspNetCore.Mvc.ViewFeatures.Test/ViewFeatures/ViewDataDictionaryOfTModelTest.cs
+++ b/test/Microsoft.AspNetCore.Mvc.ViewFeatures.Test/ViewFeatures/ViewDataDictionaryOfTModelTest.cs
@@ -26,7 +26,7 @@ namespace Microsoft.AspNetCore.Mvc.ViewFeatures
             Assert.NotNull(viewData.TemplateInfo);
             Assert.Null(viewData.Model);
             Assert.NotNull(viewData.ModelMetadata);
-            Assert.Equal(0, viewData.Count);
+            Assert.Empty(viewData);
         }
 
         [Fact]
diff --git a/test/Microsoft.AspNetCore.Mvc.ViewFeatures.Test/ViewFeatures/ViewDataDictionaryTest.cs b/test/Microsoft.AspNetCore.Mvc.ViewFeatures.Test/ViewFeatures/ViewDataDictionaryTest.cs
index 29119ffa75..cfcb4bf426 100644
--- a/test/Microsoft.AspNetCore.Mvc.ViewFeatures.Test/ViewFeatures/ViewDataDictionaryTest.cs
+++ b/test/Microsoft.AspNetCore.Mvc.ViewFeatures.Test/ViewFeatures/ViewDataDictionaryTest.cs
@@ -27,7 +27,7 @@ namespace Microsoft.AspNetCore.Mvc.ViewFeatures
             Assert.NotNull(viewData.TemplateInfo);
             Assert.Null(viewData.Model);
             Assert.NotNull(viewData.ModelMetadata);
-            Assert.Equal(0, viewData.Count);
+            Assert.Empty(viewData);
         }
 
         [Fact]
@@ -45,7 +45,7 @@ namespace Microsoft.AspNetCore.Mvc.ViewFeatures
             Assert.NotNull(viewData.TemplateInfo);
             Assert.Null(viewData.Model);
             Assert.NotNull(viewData.ModelMetadata);
-            Assert.Equal(0, viewData.Count);
+            Assert.Empty(viewData);
         }
 
         [Fact]
diff --git a/test/Microsoft.AspNetCore.Mvc.ViewFeatures.Test/ViewFeatures/ViewDataOfTTest.cs b/test/Microsoft.AspNetCore.Mvc.ViewFeatures.Test/ViewFeatures/ViewDataOfTTest.cs
index 6297e7e0c8..3e3dbaf198 100644
--- a/test/Microsoft.AspNetCore.Mvc.ViewFeatures.Test/ViewFeatures/ViewDataOfTTest.cs
+++ b/test/Microsoft.AspNetCore.Mvc.ViewFeatures.Test/ViewFeatures/ViewDataOfTTest.cs
@@ -56,7 +56,7 @@ namespace Microsoft.AspNetCore.Mvc.ViewFeatures
 
             // Act & Assert
             Assert.Empty(viewData);
-            Assert.Equal(0, viewData.Count);
+            Assert.Empty(viewData);
             Assert.False(viewData.IsReadOnly);
 
             Assert.NotNull(viewData.Keys);