Declare out variables inline, and use discards (#873)

shared/Microsoft.AspNetCore.Routing.DecisionTree.Sources/DecisionTreeBuilder.cs

@@ -125,15 +125,13 @@ namespace Microsoft.AspNetCore.Routing.DecisionTree
 
                     unsatisfiedCriteria++;
 
-                    Criterion criterion;
+                    if (!criteria.TryGetValue(kvp.Key, out var criterion))
-                    if (!criteria.TryGetValue(kvp.Key, out criterion))
                     {
                         criterion = new Criterion(comparer);
                         criteria.Add(kvp.Key, criterion);
                     }
 
-                    List<ItemDescriptor<TItem>> branch;
+                    if (!criterion.TryGetValue(kvp.Value, out var branch))
-                    if (!criterion.TryGetValue(kvp.Value, out branch))
                     {
                         branch = new List<ItemDescriptor<TItem>>();
                         criterion.Add(kvp.Value, branch);

src/Microsoft.AspNetCore.Routing/Constraints/BoolRouteConstraint.cs

@@ -30,17 +30,15 @@ namespace Microsoft.AspNetCore.Routing.Constraints
                 throw new ArgumentNullException(nameof(values));
             }
 
-            object value;
+            if (values.TryGetValue(routeKey, out var value) && value != null)
-            if (values.TryGetValue(routeKey, out value) && value != null)
             {
                 if (value is bool)
                 {
                     return true;
                 }
 
-                bool result;
                 var valueString = Convert.ToString(value, CultureInfo.InvariantCulture);
-                return bool.TryParse(valueString, out result);
+                return bool.TryParse(valueString, out _);
             }
 
             return false;

src/Microsoft.AspNetCore.Routing/Constraints/DateTimeRouteConstraint.cs

@@ -36,17 +36,15 @@ namespace Microsoft.AspNetCore.Routing.Constraints
                 throw new ArgumentNullException(nameof(values));
             }
 
-            object value;
+            if (values.TryGetValue(routeKey, out var value) && value != null)
-            if (values.TryGetValue(routeKey, out value) && value != null)
             {
                 if (value is DateTime)
                 {
                     return true;
                 }
 
-                DateTime result;
                 var valueString = Convert.ToString(value, CultureInfo.InvariantCulture);
-                return DateTime.TryParse(valueString, CultureInfo.InvariantCulture, DateTimeStyles.None, out result);
+                return DateTime.TryParse(valueString, CultureInfo.InvariantCulture, DateTimeStyles.None, out _);
             }
 
             return false;

src/Microsoft.AspNetCore.Routing/Constraints/DecimalRouteConstraint.cs

@@ -30,17 +30,15 @@ namespace Microsoft.AspNetCore.Routing.Constraints
                 throw new ArgumentNullException(nameof(values));
             }
 
-            object value;
+            if (values.TryGetValue(routeKey, out var value) && value != null)
-            if (values.TryGetValue(routeKey, out value) && value != null)
             {
                 if (value is decimal)
                 {
                     return true;
                 }
 
-                decimal result;
                 var valueString = Convert.ToString(value, CultureInfo.InvariantCulture);
-                return decimal.TryParse(valueString, NumberStyles.Number, CultureInfo.InvariantCulture, out result);
+                return decimal.TryParse(valueString, NumberStyles.Number, CultureInfo.InvariantCulture, out _);
             }
 
             return false;

src/Microsoft.AspNetCore.Routing/Constraints/DoubleRouteConstraint.cs

@@ -30,21 +30,19 @@ namespace Microsoft.AspNetCore.Routing.Constraints
                 throw new ArgumentNullException(nameof(values));
             }
 
-            object value;
+            if (values.TryGetValue(routeKey, out var value) && value != null)
-            if (values.TryGetValue(routeKey, out value) && value != null)
             {
                 if (value is double)
                 {
                     return true;
                 }
 
-                double result;
                 var valueString = Convert.ToString(value, CultureInfo.InvariantCulture);
                 return double.TryParse(
                     valueString,
                     NumberStyles.Float | NumberStyles.AllowThousands,
                     CultureInfo.InvariantCulture,
-                    out result);
+                    out _);
             }
 
             return false;

src/Microsoft.AspNetCore.Routing/Constraints/FloatRouteConstraint.cs

@@ -30,21 +30,19 @@ namespace Microsoft.AspNetCore.Routing.Constraints
                 throw new ArgumentNullException(nameof(values));
             }
 
-            object value;
+            if (values.TryGetValue(routeKey, out var value) && value != null)
-            if (values.TryGetValue(routeKey, out value) && value != null)
             {
                 if (value is float)
                 {
                     return true;
                 }
 
-                float result;
                 var valueString = Convert.ToString(value, CultureInfo.InvariantCulture);
                 return float.TryParse(
                     valueString,
                     NumberStyles.Float | NumberStyles.AllowThousands,
                     CultureInfo.InvariantCulture,
-                    out result);
+                    out _);
             }
 
             return false;

src/Microsoft.AspNetCore.Routing/Constraints/GuidRouteConstraint.cs

@@ -32,17 +32,15 @@ namespace Microsoft.AspNetCore.Routing.Constraints
                 throw new ArgumentNullException(nameof(values));
             }
 
-            object value;
+            if (values.TryGetValue(routeKey, out var value) && value != null)
-            if (values.TryGetValue(routeKey, out value) && value != null)
             {
                 if (value is Guid)
                 {
                     return true;
                 }
 
-                Guid result;
                 var valueString = Convert.ToString(value, CultureInfo.InvariantCulture);
-                return Guid.TryParse(valueString, out result);
+                return Guid.TryParse(valueString, out _);
             }
 
             return false;

src/Microsoft.AspNetCore.Routing/Constraints/HttpMethodRouteConstraint.cs

@@ -76,8 +76,7 @@ namespace Microsoft.AspNetCore.Routing.Constraints
                     // signal that he is generating a URI that will be used for an HTTP POST, so he wants the URI
                     // generation to be performed by the (b) route instead of the (a) route, consistent with what would
                     // happen on incoming requests.
-                    object obj;
+                    if (!values.TryGetValue(routeKey, out var obj))
-                    if (!values.TryGetValue(routeKey, out obj))
                     {
                         return true;
                     }

src/Microsoft.AspNetCore.Routing/Constraints/IntRouteConstraint.cs

@@ -30,17 +30,15 @@ namespace Microsoft.AspNetCore.Routing.Constraints
                 throw new ArgumentNullException(nameof(values));
             }
 
-            object value;
+            if (values.TryGetValue(routeKey, out var value) && value != null)
-            if (values.TryGetValue(routeKey, out value) && value != null)
             {
                 if (value is int)
                 {
                     return true;
                 }
 
-                int result;
                 var valueString = Convert.ToString(value, CultureInfo.InvariantCulture);
-                return int.TryParse(valueString, NumberStyles.Integer, CultureInfo.InvariantCulture, out result);
+                return int.TryParse(valueString, NumberStyles.Integer, CultureInfo.InvariantCulture, out _);
             }
 
             return false;

src/Microsoft.AspNetCore.Routing/Constraints/LengthRouteConstraint.cs

@@ -87,8 +87,7 @@ namespace Microsoft.AspNetCore.Routing.Constraints
                 throw new ArgumentNullException(nameof(values));
             }
 
-            object value;
+            if (values.TryGetValue(routeKey, out var value) && value != null)
-            if (values.TryGetValue(routeKey, out value) && value != null)
             {
                 var valueString = Convert.ToString(value, CultureInfo.InvariantCulture);
                 var length = valueString.Length;

src/Microsoft.AspNetCore.Routing/Constraints/LongRouteConstraint.cs

@@ -30,17 +30,15 @@ namespace Microsoft.AspNetCore.Routing.Constraints
                 throw new ArgumentNullException(nameof(values));
             }
 
-            object value;
+            if (values.TryGetValue(routeKey, out var value) && value != null)
-            if (values.TryGetValue(routeKey, out value) && value != null)
             {
                 if (value is long)
                 {
                     return true;
                 }
 
-                long result;
                 var valueString = Convert.ToString(value, CultureInfo.InvariantCulture);
-                return long.TryParse(valueString, NumberStyles.Integer, CultureInfo.InvariantCulture, out result);
+                return long.TryParse(valueString, NumberStyles.Integer, CultureInfo.InvariantCulture, out _);
             }
 
             return false;

src/Microsoft.AspNetCore.Routing/Constraints/MaxLengthRouteConstraint.cs

@@ -50,8 +50,7 @@ namespace Microsoft.AspNetCore.Routing.Constraints
                 throw new ArgumentNullException(nameof(values));
             }
 
-            object value;
+            if (values.TryGetValue(routeKey, out var value) && value != null)
-            if (values.TryGetValue(routeKey, out value) && value != null)
             {
                 var valueString = Convert.ToString(value, CultureInfo.InvariantCulture);
                 return valueString.Length <= MaxLength;

src/Microsoft.AspNetCore.Routing/Constraints/MaxRouteConstraint.cs

@@ -44,12 +44,10 @@ namespace Microsoft.AspNetCore.Routing.Constraints
                 throw new ArgumentNullException(nameof(values));
             }
 
-            object value;
+            if (values.TryGetValue(routeKey, out var value) && value != null)
-            if (values.TryGetValue(routeKey, out value) && value != null)
             {
-                long longValue;
                 var valueString = Convert.ToString(value, CultureInfo.InvariantCulture);
-                if (long.TryParse(valueString, NumberStyles.Integer, CultureInfo.InvariantCulture, out longValue))
+                if (long.TryParse(valueString, NumberStyles.Integer, CultureInfo.InvariantCulture, out var longValue))
                 {
                     return longValue <= Max;
                 }

src/Microsoft.AspNetCore.Routing/Constraints/MinLengthRouteConstraint.cs

@@ -50,8 +50,7 @@ namespace Microsoft.AspNetCore.Routing.Constraints
                 throw new ArgumentNullException(nameof(values));
             }
 
-            object value;
+            if (values.TryGetValue(routeKey, out var value) && value != null)
-            if (values.TryGetValue(routeKey, out value) && value != null)
             {
                 var valueString = Convert.ToString(value, CultureInfo.InvariantCulture);
                 return valueString.Length >= MinLength;

src/Microsoft.AspNetCore.Routing/Constraints/MinRouteConstraint.cs

@@ -44,12 +44,10 @@ namespace Microsoft.AspNetCore.Routing.Constraints
                 throw new ArgumentNullException(nameof(values));
             }
 
-            object value;
+            if (values.TryGetValue(routeKey, out var value) && value != null)
-            if (values.TryGetValue(routeKey, out value) && value != null)
             {
-                long longValue;
                 var valueString = Convert.ToString(value, CultureInfo.InvariantCulture);
-                if (long.TryParse(valueString, NumberStyles.Integer, CultureInfo.InvariantCulture, out longValue))
+                if (long.TryParse(valueString, NumberStyles.Integer, CultureInfo.InvariantCulture, out var longValue))
                 {
                     return longValue >= Min;
                 }

src/Microsoft.AspNetCore.Routing/Constraints/OptionalRouteConstraint.cs

@@ -40,8 +40,7 @@ namespace Microsoft.AspNetCore.Routing.Constraints
                 throw new ArgumentNullException(nameof(values));
             }
 
-            object value;
+            if (values.TryGetValue(routeKey, out var value))
-            if (values.TryGetValue(routeKey, out value))
             {
                 return InnerConstraint.Match(httpContext,
                                              route,

src/Microsoft.AspNetCore.Routing/Constraints/RangeRouteConstraint.cs

@@ -58,12 +58,10 @@ namespace Microsoft.AspNetCore.Routing.Constraints
                 throw new ArgumentNullException(nameof(values));
             }
 
-            object value;
+            if (values.TryGetValue(routeKey, out var value) && value != null)
-            if (values.TryGetValue(routeKey, out value) && value != null)
             {
-                long longValue;
                 var valueString = Convert.ToString(value, CultureInfo.InvariantCulture);
-                if (Int64.TryParse(valueString, NumberStyles.Integer, CultureInfo.InvariantCulture, out longValue))
+                if (long.TryParse(valueString, NumberStyles.Integer, CultureInfo.InvariantCulture, out var longValue))
                 {
                     return longValue >= Min && longValue <= Max;
                 }

src/Microsoft.AspNetCore.Routing/Constraints/RegexRouteConstraint.cs

@@ -54,9 +54,7 @@ namespace Microsoft.AspNetCore.Routing.Constraints
                 throw new ArgumentNullException(nameof(values));
             }
 
-            object routeValue;
+            if (values.TryGetValue(routeKey, out var routeValue)
-
-            if (values.TryGetValue(routeKey, out routeValue)
                 && routeValue != null)
             {
                 var parameterValueString = Convert.ToString(routeValue, CultureInfo.InvariantCulture);

src/Microsoft.AspNetCore.Routing/Constraints/RequiredRouteConstraint.cs

@@ -34,8 +34,7 @@ namespace Microsoft.AspNetCore.Routing.Constraints
                 throw new ArgumentNullException(nameof(values));
             }
 
-            object value;
+            if (values.TryGetValue(routeKey, out var value) && value != null)
-            if (values.TryGetValue(routeKey, out value) && value != null)
             {
                 // In routing the empty string is equivalent to null, which is equivalent to an unset value.
                 var valueString = Convert.ToString(value, CultureInfo.InvariantCulture);

src/Microsoft.AspNetCore.Routing/Constraints/StringRouteConstraint.cs

@@ -41,9 +41,7 @@ namespace Microsoft.AspNetCore.Routing.Constraints
                 throw new ArgumentNullException(nameof(values));
             }
 
-            object routeValue;
+            if (values.TryGetValue(routeKey, out var routeValue)
-
-            if (values.TryGetValue(routeKey, out routeValue)
                 && routeValue != null)
             {
                 var parameterValueString = Convert.ToString(routeValue, CultureInfo.InvariantCulture);

src/Microsoft.AspNetCore.Routing/Internal/LinkGenerationDecisionTree.cs

@@ -87,11 +87,9 @@ namespace Microsoft.AspNetCore.Routing.Internal
                 var criterion = node.Criteria[i];
                 var key = criterion.Key;
 
-                object value;
+                if (values.TryGetValue(key, out var value))
-                if (values.TryGetValue(key, out value))
                 {
-                    DecisionTreeNode<OutboundMatch> branch;
+                    if (criterion.Branches.TryGetValue(value ?? string.Empty, out var branch))
-                    if (criterion.Branches.TryGetValue(value ?? string.Empty, out branch))
                     {
                         Walk(results, values, ambientValues, branch, isFallbackPath);
                     }

src/Microsoft.AspNetCore.Routing/RouteCollection.cs

@@ -91,8 +91,8 @@ namespace Microsoft.AspNetCore.Routing
             if (!string.IsNullOrEmpty(context.RouteName))
             {
                 VirtualPathData namedRoutePathData = null;
-                INamedRouter matchedNamedRoute;
+
-                if (_namedRoutes.TryGetValue(context.RouteName, out matchedNamedRoute))
+                if (_namedRoutes.TryGetValue(context.RouteName, out var matchedNamedRoute))
                 {
                     namedRoutePathData = matchedNamedRoute.GetVirtualPath(context);
                 }

src/Microsoft.AspNetCore.Routing/RouteConstraintBuilder.cs

@@ -184,8 +184,7 @@ namespace Microsoft.AspNetCore.Routing
 
         private void Add(string key, IRouteConstraint constraint)
         {
-            List<IRouteConstraint> list;
+            if (!_constraints.TryGetValue(key, out var list))
-            if (!_constraints.TryGetValue(key, out list))
             {
                 list = new List<IRouteConstraint>();
                 _constraints.Add(key, list);

src/Microsoft.AspNetCore.Routing/RouteConstraintMatcher.cs

@@ -51,8 +51,7 @@ namespace Microsoft.AspNetCore.Routing
                 {
                     if (routeDirection.Equals(RouteDirection.IncomingRequest))
                     {
-                        object routeValue;
+                        routeValues.TryGetValue(kvp.Key, out var routeValue);
-                        routeValues.TryGetValue(kvp.Key, out routeValue);
 
                         logger.RouteValueDoesNotMatchConstraint(routeValue, kvp.Key, kvp.Value);
                     }

src/Microsoft.AspNetCore.Routing/Template/TemplateMatcher.cs

@@ -49,8 +49,7 @@ namespace Microsoft.AspNetCore.Routing.Template
                     continue;
                 }
 
-                object value;
+                if (Defaults.TryGetValue(part.Name, out var value))
-                if (Defaults.TryGetValue(part.Name, out value))
                 {
                     _hasDefaultValue[i] = true;
                     _defaultValues[i] = value;

src/Microsoft.AspNetCore.Routing/Tree/TreeEnumerator.cs

@@ -91,9 +91,8 @@ namespace Microsoft.AspNetCore.Routing.Tree
 
                 if (next.Literals.Count > 0)
                 {
-                    UrlMatchingNode node;
                     Debug.Assert(next.Depth < _tokenizer.Count);
-                    if (next.Literals.TryGetValue(_tokenizer[next.Depth].Value, out node))
+                    if (next.Literals.TryGetValue(_tokenizer[next.Depth].Value, out var node))
                     {
                         _stack.Push(node);
                     }

src/Microsoft.AspNetCore.Routing/Tree/TreeRouteBuilder.cs

@@ -259,8 +259,7 @@ namespace Microsoft.AspNetCore.Routing.Tree
 
             foreach (var entry in InboundEntries)
             {
-                UrlMatchingTree tree;
+                if (!trees.TryGetValue(entry.Order, out var tree))
-                if (!trees.TryGetValue(entry.Order, out tree))
                 {
                     tree = new UrlMatchingTree(entry.Order);
                     trees.Add(entry.Order, tree);

src/Microsoft.AspNetCore.Routing/Tree/TreeRouter.cs

@@ -103,8 +103,7 @@ namespace Microsoft.AspNetCore.Routing.Tree
                 // We only need to keep one OutboundMatch per route template
                 // so in case two entries have the same name and the same template we only keep
                 // the first entry.
-                OutboundMatch namedMatch;
+                if (_namedEntries.TryGetValue(entry.RouteName, out var namedMatch) &&
-                if (_namedEntries.TryGetValue(entry.RouteName, out namedMatch) &&
                     !string.Equals(
                         namedMatch.Entry.RouteTemplate.TemplateText,
                         entry.RouteTemplate.TemplateText,
@@ -233,8 +232,7 @@ namespace Microsoft.AspNetCore.Routing.Tree
 
         private VirtualPathData GetVirtualPathForNamedRoute(VirtualPathContext context)
         {
-            OutboundMatch match;
+            if (_namedEntries.TryGetValue(context.RouteName, out var match))
-            if (_namedEntries.TryGetValue(context.RouteName, out match))
             {
                 var path = GenerateVirtualPath(context, match.Entry, match.TemplateBinder);
                 if (path != null)

src/Microsoft.AspNetCore.Routing/Tree/UrlMatchingTree.cs

@@ -86,8 +86,7 @@ namespace Microsoft.AspNetCore.Routing.Tree
                 var part = segment.Parts[0];
                 if (part.IsLiteral)
                 {
-                    UrlMatchingNode next;
+                    if (!current.Literals.TryGetValue(part.Text, out var next))
-                    if (!current.Literals.TryGetValue(part.Text, out next))
                     {
                         next = new UrlMatchingNode(length: i + 1);
                         current.Literals.Add(part.Text, next);