Use SourceText.ToString directly instead of GetSubTextString extension method.

src/Razor/src/Microsoft.CodeAnalysis.Razor.Workspaces/CodeActions/CSharp/TypeAccessibilityCodeActionProvider.cs

@@ -111,7 +111,7 @@ private static ImmutableArray<RazorVSInternalCodeAction> ProcessCodeActionsVSCod
                     continue;
                 }
 
-                var associatedValue = context.SourceText.GetSubTextString(diagnosticSpan);
+                var associatedValue = context.SourceText.ToString(diagnosticSpan);
 
                 var fqn = string.Empty;
 

src/Razor/src/Microsoft.CodeAnalysis.Razor.Workspaces/CodeActions/Razor/ExtractToCodeBehindCodeActionResolver.cs

@@ -46,7 +46,7 @@ internal class ExtractToCodeBehindCodeActionResolver(
         var text = await documentContext.GetSourceTextAsync(cancellationToken).ConfigureAwait(false);
 
         var className = Path.GetFileNameWithoutExtension(path);
-        var codeBlockContent = text.GetSubTextString(new TextSpan(actionParams.ExtractStart, actionParams.ExtractEnd - actionParams.ExtractStart)).Trim();
+        var codeBlockContent = text.ToString(new TextSpan(actionParams.ExtractStart, actionParams.ExtractEnd - actionParams.ExtractStart)).Trim();
         var codeBehindContent = GenerateCodeBehindClass(className, actionParams.Namespace, codeBlockContent, codeDocument);
 
         codeBehindContent = await _roslynCodeActionHelpers.GetFormattedNewFileContentsAsync(documentContext.Project, codeBehindUri, codeBehindContent, cancellationToken).ConfigureAwait(false);

src/Razor/src/Microsoft.CodeAnalysis.Razor.Workspaces/CodeActions/Razor/ExtractToCssCodeActionResolver.cs

@@ -42,7 +42,7 @@ internal class ExtractToCssCodeActionResolver(
 
         var text = await documentContext.GetSourceTextAsync(cancellationToken).ConfigureAwait(false);
 
-        var cssContent = text.GetSubTextString(new TextSpan(actionParams.ExtractStart, actionParams.ExtractEnd - actionParams.ExtractStart)).Trim();
+        var cssContent = text.ToString(new TextSpan(actionParams.ExtractStart, actionParams.ExtractEnd - actionParams.ExtractStart)).Trim();
         var removeRange = codeDocument.Source.Text.GetRange(actionParams.RemoveStart, actionParams.RemoveEnd);
 
         var codeDocumentIdentifier = new OptionalVersionedTextDocumentIdentifier { DocumentUri = new(documentContext.Uri) };

src/Razor/src/Microsoft.CodeAnalysis.Razor.Workspaces/CodeActions/Razor/PromoteUsingCodeActionResolver.cs

@@ -43,7 +43,7 @@ internal class PromoteUsingCodeActionResolver(IFileSystem fileSystem) : IRazorCo
 
         using var edits = new PooledArrayBuilder<SumType<TextDocumentEdit, CreateFile, RenameFile, DeleteFile>>();
 
-        var textToInsert = sourceText.GetSubTextString(TextSpan.FromBounds(actionParams.UsingStart, actionParams.UsingEnd));
+        var textToInsert = sourceText.ToString(TextSpan.FromBounds(actionParams.UsingStart, actionParams.UsingEnd));
         var insertLocation = new LinePosition(0, 0);
         if (!_fileSystem.FileExists(importsFile))
         {

src/Razor/src/Microsoft.CodeAnalysis.Razor.Workspaces/Extensions/SourceTextExtensions.cs

@@ -2,7 +2,6 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 
 using System;
-using System.Buffers;
 using System.Collections.Generic;
 using System.Collections.Immutable;
 using Microsoft.AspNetCore.Razor;
@@ -52,14 +51,6 @@ public static int GetPosition(this SourceText text, LinePosition position)
     public static int GetPosition(this SourceText text, int line, int character)
         => text.GetPosition(new LinePosition(line, character));
 
-    public static string GetSubTextString(this SourceText text, TextSpan span)
-    {
-        using var _ = ArrayPool<char>.Shared.GetPooledArray(span.Length, out var charBuffer);
-
-        text.CopyTo(span.Start, charBuffer, 0, span.Length);
-        return new string(charBuffer, 0, span.Length);
-    }
-
     public static bool NonWhitespaceContentEquals(this SourceText text, ImmutableArray<TextChange> changes)
     {
         if (changes.IsEmpty)

src/Razor/src/Microsoft.CodeAnalysis.Razor.Workspaces/FindAllReferences/FindAllReferencesHelper.cs

@@ -45,7 +45,7 @@ internal static class FindAllReferencesHelper
                 !documentMappingService.TryMapToCSharpDocumentPosition(csharpDocument, line.End, out _, out _))
             {
                 var start = line.GetFirstNonWhitespacePosition() ?? line.Start;
-                return codeDoc.Source.Text.GetSubTextString(TextSpan.FromBounds(start, line.End));
+                return codeDoc.Source.Text.ToString(TextSpan.FromBounds(start, line.End));
             }
         }
 

src/Razor/src/Microsoft.CodeAnalysis.Razor.Workspaces/Formatting/AddUsingsHelper.cs

@@ -140,7 +140,7 @@ static string GetNamespaceFromDirective(UsingDirectiveSyntax usingDirectiveSynta
             // as trivia to the using keyword.
             var start = usingDirectiveSyntax.UsingKeyword.FullSpan.End;
 
-            return sourceText.GetSubTextString(TextSpan.FromBounds(start, end));
+            return sourceText.ToString(TextSpan.FromBounds(start, end));
         }
     }
 

src/Razor/src/Microsoft.CodeAnalysis.Razor.Workspaces/Formatting/FormattingUtilities.cs

@@ -167,7 +167,7 @@ public static int GetIndentationLevel(TextLine line, int firstNonWhitespaceChara
             else
             {
                 Debug.Assert(text[i] == ' ');
-                additionalIndentation = text.GetSubTextString(TextSpan.FromBounds(i, firstNonWhitespaceCharacterPosition));
+                additionalIndentation = text.ToString(TextSpan.FromBounds(i, firstNonWhitespaceCharacterPosition));
                 return tabCount;
             }
         }
@@ -222,7 +222,7 @@ public static string GetIndentationString(int indentation, bool insertSpaces, in
     /// </summary>
     public static void NaivelyUnindentSubstring(SourceText text, TextSpan extractionSpan, System.Text.StringBuilder builder)
     {
-        var extractedText = text.GetSubTextString(extractionSpan);
+        var extractedText = text.ToString(extractionSpan);
         var range = text.GetRange(extractionSpan);
         if (range.Start.Line == range.End.Line)
         {

src/Razor/src/Microsoft.CodeAnalysis.Razor.Workspaces/Formatting/Passes/CSharpFormattingPass.CSharpDocumentGenerator.cs

@@ -279,13 +279,13 @@ private void AddAdditionalLineFormattingContent(StringBuilder additionalLinesBui
                 {
                     additionalLinesBuilder.AppendLine("F<");
                     additionalLinesBuilder.AppendLine(GetAdditionalLineComment(originalSpan));
-                    additionalLinesBuilder.AppendLine(_sourceText.GetSubTextString(originalSpan.ToTextSpan()));
+                    additionalLinesBuilder.AppendLine(_sourceText.ToString(originalSpan.ToTextSpan()));
                     additionalLinesBuilder.AppendLine("> x;");
                     return;
                 }
 
                 additionalLinesBuilder.AppendLine(GetAdditionalLineComment(originalSpan));
-                additionalLinesBuilder.AppendLine(_sourceText.GetSubTextString(originalSpan.ToTextSpan()));
+                additionalLinesBuilder.AppendLine(_sourceText.ToString(originalSpan.ToTextSpan()));
                 additionalLinesBuilder.AppendLine(";");
             }
 
@@ -337,7 +337,7 @@ _sourceText.Lines[nodeStartLine] is { } previousLine &&
                     // This is a multi-line literal, and we're emiting the 2nd line, and the literal didn't start at the start of
                     // the previous line, so it wouldn't have been handled by that lines formatting. We need to include it here,
                     // but skip it to not confuse things.
-                    _builder.AppendLine(_sourceText.GetSubTextString(TextSpan.FromBounds(node.SpanStart, previousLine.End)));
+                    _builder.AppendLine(_sourceText.ToString(TextSpan.FromBounds(node.SpanStart, previousLine.End)));
                     skipPreviousLine = true;
                 }
 
@@ -907,8 +907,8 @@ private LineInfo VisitCSharpCodeBlock(RazorSyntaxNode node, CSharpCodeBlockSynta
 
                 // Multi-line expressions are often not formatted by Roslyn much at all, but it will often move subsequent lines
                 // relative to the first, so make sure we include the users indentation so everything moves together, and is stable.
-                _builder.Append(_sourceText.GetSubTextString(TextSpan.FromBounds(_currentLine.Start, _currentFirstNonWhitespacePosition)));
-                _builder.AppendLine(_sourceText.GetSubTextString(TextSpan.FromBounds(_currentToken.Position + 1, _currentLine.End)));
+                _builder.Append(_sourceText.ToString(TextSpan.FromBounds(_currentLine.Start, _currentFirstNonWhitespacePosition)));
+                _builder.AppendLine(_sourceText.ToString(TextSpan.FromBounds(_currentToken.Position + 1, _currentLine.End)));
                 return CreateLineInfo(
                     processFormatting: true,
                     checkForNewLines: true,
@@ -919,7 +919,7 @@ private LineInfo VisitCSharpCodeBlock(RazorSyntaxNode node, CSharpCodeBlockSynta
             public override LineInfo VisitCSharpCodeBlock(CSharpCodeBlockSyntax node)
             {
                 // Matches things like @if, so skip the first character, but output as C# otherwise
-                _builder.AppendLine(_sourceText.GetSubTextString(TextSpan.FromBounds(_currentToken.Position + 1, _currentLine.End)));
+                _builder.AppendLine(_sourceText.ToString(TextSpan.FromBounds(_currentToken.Position + 1, _currentLine.End)));
 
                 return CreateLineInfo(
                     processFormatting: true,
@@ -1008,7 +1008,7 @@ private LineInfo VisitUsingDirective()
                 // For @using we just skip over the @ and format as a C# using directive
                 // "@using System" to "using System"
                 // Roslyn's parser is smart enough to not care about missing semicolons.
-                _builder.AppendLine(_sourceText.GetSubTextString(TextSpan.FromBounds(_currentToken.Position + 1, _currentLine.End)));
+                _builder.AppendLine(_sourceText.ToString(TextSpan.FromBounds(_currentToken.Position + 1, _currentLine.End)));
                 return CreateLineInfo(
                     processFormatting: true,
                     originOffset: 1,

src/Razor/src/Microsoft.CodeAnalysis.Razor.Workspaces/Formatting/Passes/CSharpOnTypeFormattingPass.cs

@@ -587,7 +587,7 @@ private async Task<ImmutableArray<TextChange>> AdjustIndentationAsync(Formatting
         {
             var mappingSpan = new TextSpan(mapping.OriginalSpan.AbsoluteIndex, mapping.OriginalSpan.Length);
 #if DEBUG
-            var spanText = context.SourceText.GetSubTextString(mappingSpan);
+            var spanText = context.SourceText.ToString(mappingSpan);
 #endif
 
             var options = new ShouldFormatOptions(

src/Razor/src/Microsoft.CodeAnalysis.Razor.Workspaces/Formatting/RazorFormattingService.cs

@@ -342,7 +342,7 @@ internal static TextChange MergeChanges(ImmutableArray<TextChange> changes, Sour
         var affectedRange = changedText.GetEncompassingTextChangeRange(sourceText);
         var spanBeforeChange = affectedRange.Span;
         var spanAfterChange = new TextSpan(spanBeforeChange.Start, affectedRange.NewLength);
-        var newText = changedText.GetSubTextString(spanAfterChange);
+        var newText = changedText.ToString(spanAfterChange);
 
         return new TextChange(spanBeforeChange, newText);
     }

src/Razor/test/Microsoft.AspNetCore.Razor.LanguageServer.Test/CodeActions/Razor/ExtractToComponentCodeActionProviderTest.cs

@@ -698,8 +698,8 @@ private async Task TestAsync(string contents)
 
         if (resultSpan.Start != actionParams.Start || resultSpan.End != actionParams.End)
         {
-            var resultText = context.SourceText.GetSubTextString(resultSpan);
-            var actualText = context.SourceText.GetSubTextString(TextSpan.FromBounds(actionParams.Start, actionParams.End));
+            var resultText = context.SourceText.ToString(resultSpan);
+            var actualText = context.SourceText.ToString(TextSpan.FromBounds(actionParams.Start, actionParams.End));
             AssertEx.EqualOrDiff(resultText, actualText, "Code action span does not match expected");
         }
     }

src/Razor/test/Microsoft.AspNetCore.Razor.LanguageServer.Test/Diagnostics/RazorDiagnosticHelperTest.cs

@@ -70,7 +70,7 @@ public void ConvertSpanToRange_ReturnsConvertedRange()
         var range = RazorDiagnosticHelper.ConvertSpanToRange(sourceSpan, sourceText);
 
         // Assert
-        Assert.Equal("lo W", sourceText.GetSubTextString(sourceText.GetTextSpan(range)));
+        Assert.Equal("lo W", sourceText.ToString(sourceText.GetTextSpan(range)));
         Assert.Equal(expectedRange, range);
     }
 
@@ -86,7 +86,7 @@ public void ConvertSpanToRange_StartsOutsideOfDocument_EmptyDocument_NormalizesT
         var range = RazorDiagnosticHelper.ConvertSpanToRange(sourceSpan, sourceText);
 
         // Assert
-        Assert.Equal("", sourceText.GetSubTextString(sourceText.GetTextSpan(range)));
+        Assert.Equal("", sourceText.ToString(sourceText.GetTextSpan(range)));
         Assert.Equal(expectedRange, range);
     }
 
@@ -102,7 +102,7 @@ public void ConvertSpanToRange_StartsOutsideOfDocument_NormalizesToEnd()
         var range = RazorDiagnosticHelper.ConvertSpanToRange(sourceSpan, sourceText);
 
         // Assert
-        Assert.Equal("", sourceText.GetSubTextString(sourceText.GetTextSpan(range)));
+        Assert.Equal("", sourceText.ToString(sourceText.GetTextSpan(range)));
         Assert.Equal(expectedRange, range);
     }
 
@@ -118,7 +118,7 @@ public void ConvertSpanToRange_EndsOutsideOfDocument_NormalizesToEnd()
         var range = RazorDiagnosticHelper.ConvertSpanToRange(sourceSpan, sourceText);
 
         // Assert
-        Assert.Equal("World", sourceText.GetSubTextString(sourceText.GetTextSpan(range)));
+        Assert.Equal("World", sourceText.ToString(sourceText.GetTextSpan(range)));
         Assert.Equal(expectedRange, range);
     }
 

src/Razor/test/Microsoft.AspNetCore.Razor.LanguageServer.Test/Semantic/SemanticTokensTest.cs

@@ -1132,7 +1132,7 @@ private static string GetFileRepresentationOfTokens(SourceText sourceText, int[]
             builder.Append(length).Append(' ');
             builder.Append(typeString).Append(' ');
             builder.Append(data[i + 4]).Append(' ');
-            builder.Append('[').Append(sourceText.GetSubTextString(new TextSpan(sourceText.Lines[lineIndex].Start + lineOffset, length))).Append(']');
+            builder.Append('[').Append(sourceText.ToString(new TextSpan(sourceText.Lines[lineIndex].Start + lineOffset, length))).Append(']');
             builder.AppendLine();
 
             prevLength = length;

src/Razor/test/Microsoft.VisualStudio.LanguageServices.Razor.Test/Cohost/RemoteDebugInfoServiceTest.cs

@@ -381,7 +381,7 @@ private async Task VerifyProximityExpressionsAsync(TestCode input, string[] extr
 
         Assert.NotNull(result);
 
-        var expected = input.Spans.Select(inputText.GetSubTextString).Concat(extraExpressions).OrderAsArray();
+        var expected = input.Spans.Select(inputText.ToString).Concat(extraExpressions).OrderAsArray();
         AssertEx.SequenceEqual(expected, result.OrderAsArray());
     }
 

src/Razor/test/Microsoft.VisualStudioCode.RazorExtension.Test/Endpoints/Shared/CohostSemanticTokensRangeEndpointTest.cs

@@ -475,7 +475,7 @@ private static string GetTestOutput(SourceText sourceText, int[]? data, ISemanti
 
             var type = tokenTypes[data[i + 3]];
             var modifier = GetTokenModifierString(data[i + 4], legend);
-            var text = sourceText.GetSubTextString(new TextSpan(sourceText.Lines[lineIndex].Start + lineOffset, length));
+            var text = sourceText.ToString(new TextSpan(sourceText.Lines[lineIndex].Start + lineOffset, length));
             builder.AppendLine($"{lineDelta} {charDelta} {length} {type} {modifier} [{text}]");
 
             prevLength = length;