Improve string formatting

Author: commonsensesoftware

src/AspNetCore/WebApi/src/Asp.Versioning.Mvc.ApiExplorer/ApiDescriptionExtensions.cs

@@ -106,9 +106,14 @@ public static bool TryUpdateRelativePathAndRemoveApiVersionParameter( this ApiDe
             return false;
         }
 
-        var token = '{' + parameter.Name + '}';
+        Span<char> token = stackalloc char[parameter.Name.Length + 2];
+
+        token[0] = '{';
+        token[^1] = '}';
+        parameter.Name.AsSpan().CopyTo( token.Slice( 1, parameter.Name.Length ) );
+
         var value = apiVersion.ToString( options.SubstitutionFormat, CultureInfo.InvariantCulture );
-        var newRelativePath = relativePath.Replace( token, value, StringComparison.Ordinal );
+        var newRelativePath = relativePath.Replace( token.ToString(), value, StringComparison.Ordinal );
 
         if ( relativePath == newRelativePath )
         {

src/AspNetCore/WebApi/src/Asp.Versioning.Mvc.ApiExplorer/ApiVersionParameterDescriptionContext.cs

@@ -9,6 +9,7 @@ namespace Asp.Versioning.ApiExplorer;
 using Microsoft.AspNetCore.Routing;
 using Microsoft.AspNetCore.Routing.Patterns;
 using Microsoft.AspNetCore.Routing.Template;
+using System.Runtime.CompilerServices;
 using static Asp.Versioning.ApiVersionParameterLocation;
 using static System.Linq.Enumerable;
 using static System.StringComparison;
@@ -304,7 +305,7 @@ routeInfo.Constraints is IEnumerable<IRouteConstraint> constraints &&
                         continue;
                     }
 
-                    var token = $"{parameter.Name}:{constraintName}";
+                    var token = FormatToken( parameter.Name, constraintName );
 
                     parameterDescription.Name = parameter.Name;
                     description.RelativePath = relativePath.Replace( token, parameter.Name, Ordinal );
@@ -375,7 +376,7 @@ routeInfo.Constraints is IEnumerable<IRouteConstraint> constraints &&
                 },
                 Source = BindingSource.Path,
             };
-            var token = $"{parameter.Name}:{constraintName}";
+            var token = FormatToken( parameter.Name!, constraintName! );
 
             description.RelativePath = relativePath.Replace( token, parameter.Name, Ordinal );
             description.ParameterDescriptions.Insert( 0, result );
@@ -457,4 +458,18 @@ private static bool FirstParameterIsOptional(
 
         return apiVersion == defaultApiVersion;
     }
+
+    [MethodImpl( MethodImplOptions.AggressiveInlining )]
+    private static string FormatToken( ReadOnlySpan<char> parameterName, ReadOnlySpan<char> constraintName )
+    {
+        var left = parameterName.Length;
+        var right = constraintName.Length;
+        Span<char> token = stackalloc char[left + right + 1];
+
+        parameterName.CopyTo( token[..left] );
+        token[left] = ':';
+        constraintName.CopyTo( token.Slice( left + 1, right ) );
+
+        return token.ToString();
+    }
 }