Additional methods on ParameterCollection to simplify usage

src/Microsoft.AspNetCore.Blazor/Components/ParameterCollection.cs

@@ -2,6 +2,7 @@
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System;
+using System.Collections.Generic;
 using Microsoft.AspNetCore.Blazor.RenderTree;
 
 namespace Microsoft.AspNetCore.Blazor.Components
@@ -41,6 +42,42 @@ namespace Microsoft.AspNetCore.Blazor.Components
         public ParameterEnumerator GetEnumerator()
             => new ParameterEnumerator(_frames, _ownerIndex);
 
+        /// <summary>
+        /// Gets the value of the parameter with the specified name.
+        /// </summary>
+        /// <typeparam name="T">The type of the value.</typeparam>
+        /// <param name="parameterName">The name of the parameter.</param>
+        /// <param name="result">Receives the result, if any.</param>
+        /// <returns>True if a matching parameter was found; false otherwise.</returns>
+        public bool TryGetValue<T>(string parameterName, out T result)
+        {
+            foreach (var entry in this)
+            {
+                if (string.Equals(entry.Name, parameterName))
+                {
+                    result = (T)entry.Value;
+                    return true;
+                }
+            }
+
+            result = default;
+            return false;
+        }
+
+        /// <summary>
+        /// Returns a dictionary populated with the contents of the <see cref="ParameterCollection"/>.
+        /// </summary>
+        /// <returns>A dictionary populated with the contents of the <see cref="ParameterCollection"/>.</returns>
+        public IReadOnlyDictionary<string, object> ToDictionary()
+        {
+            var result = new Dictionary<string, object>();
+            foreach (var entry in this)
+            {
+                result[entry.Name] = entry.Value;
+            }
+            return result;
+        }
+
         // It's internal because there isn't a known use case for user code comparing
         // ParameterCollection instances, and even if there was, it's unlikely it should
         // use these equality rules which are designed for their effect on rendering.

test/Microsoft.AspNetCore.Blazor.Test/ParameterCollectionTest.cs

@@ -85,6 +85,88 @@ namespace Microsoft.AspNetCore.Blazor.Test
                 AssertParameter("attribute 2", attribute2Value));
         }
 
+        [Fact]
+        public void CanTryGetNonExistingValue()
+        {
+            // Arrange
+            var parameterCollection = new ParameterCollection(new[]
+            {
+                RenderTreeFrame.Element(0, "some element").WithElementSubtreeLength(2),
+                RenderTreeFrame.Attribute(1, "some other entry", new object())
+            }, 0);
+
+            // Act
+            var didFind = parameterCollection.TryGetValue<string>("nonexisting entry", out var value);
+
+            // Assert
+            Assert.False(didFind);
+            Assert.Null(value);
+        }
+
+        [Fact]
+        public void CanTryGetExistingValueWithCorrectType()
+        {
+            // Arrange
+            var parameterCollection = new ParameterCollection(new[]
+            {
+                RenderTreeFrame.Element(0, "some element").WithElementSubtreeLength(2),
+                RenderTreeFrame.Attribute(1, "my entry", "hello")
+            }, 0);
+
+            // Act
+            var didFind = parameterCollection.TryGetValue<string>("my entry", out var value);
+
+            // Assert
+            Assert.True(didFind);
+            Assert.Equal("hello", value);
+        }
+
+        [Fact]
+        public void ThrowsIfTryGetExistingValueWithIncorrectType()
+        {
+            // Arrange
+            var parameterCollection = new ParameterCollection(new[]
+            {
+                RenderTreeFrame.Element(0, "some element").WithElementSubtreeLength(2),
+                RenderTreeFrame.Attribute(1, "my entry", "hello")
+            }, 0);
+
+            // Act/Assert
+            Assert.Throws<InvalidCastException>(() =>
+            {
+                parameterCollection.TryGetValue<bool>("my entry", out var value);
+            });
+        }
+
+        [Fact]
+        public void CanConvertToReadOnlyDictionary()
+        {
+            // Arrange
+            var entry2Value = new object();
+            var parameterCollection = new ParameterCollection(new[]
+            {
+                RenderTreeFrame.Element(0, "some element").WithElementSubtreeLength(3),
+                RenderTreeFrame.Attribute(0, "entry 1", "value 1"),
+                RenderTreeFrame.Attribute(0, "entry 2", entry2Value),
+            }, 0);
+
+            // Act
+            IReadOnlyDictionary<string, object> dict = parameterCollection.ToDictionary();
+
+            // Assert
+            Assert.Collection(dict,
+                entry =>
+                {
+                    Assert.Equal("entry 1", entry.Key);
+                    Assert.Equal("value 1", entry.Value);
+                },
+                entry =>
+                {
+                    Assert.Equal("entry 2", entry.Key);
+                    Assert.Same(entry2Value, entry.Value);
+                });
+        }
+
         private Action<Parameter> AssertParameter(string expectedName, object expectedValue)
         {
             return parameter =>