using StringBuilderbuilder.Append(String,int,int)

Author: himgoyalmicro

src/Microsoft.DotNet.Wpf/src/PresentationFramework/System/Windows/Markup/MarkupExtensionParser.cs

@@ -1628,11 +1628,7 @@ internal static void RemoveEscapes(ref string value)
                     if (builder == null)
                     {
                         builder = new StringBuilder(value.Length);
-#if NET
-                        builder.Append(value.AsSpan(0,i));
-#else
-                        builder.Append(value.Substring(0,i));
-#endif
+                        builder.Append(value, 0, i);
                     }
                     noEscape = false;
                 }