Refine DebuggerDisplay implementations based on feedback

- Move try/catch inside #else block for Base64 validation
- Create DebuggerDisplayHelper internal class for shared base64 decoding logic
- Simplify DebuggerDisplay attribute escaping (use \" instead of \\\")
- Use DebuggerDisplayHelper in both ContentBlock types and BlobResourceContents

Co-authored-by: stephentoub <[email protected]>

Author: Copilot

src/ModelContextProtocol.Core/Protocol/BlobResourceContents.cs

@@ -35,28 +35,7 @@ private string DebuggerDisplay
     {
         get
         {
-            string lengthDisplay;
-            try
-            {
-#if NET
-                if (System.Buffers.Text.Base64.IsValid(System.Text.Encoding.UTF8.GetBytes(Blob), out int decodedLength))
-                {
-                    lengthDisplay = $"{decodedLength} bytes";
-                }
-                else
-                {
-                    lengthDisplay = "invalid base64";
-                }
-#else
-                byte[] decoded = Convert.FromBase64String(Blob);
-                lengthDisplay = $"{decoded.Length} bytes";
-#endif
-            }
-            catch
-            {
-                lengthDisplay = "invalid base64";
-            }
-
+            string lengthDisplay = DebuggerDisplayHelper.GetBase64LengthDisplay(Blob);
             string mimeInfo = MimeType is not null ? $", MimeType = {MimeType}" : "";
             return $"Uri = \"{Uri}\"{mimeInfo}, Length = {lengthDisplay}";
         }

src/ModelContextProtocol.Core/Protocol/ContentBlock.cs

@@ -32,30 +32,6 @@ private protected ContentBlock()
     {
     }
 
-    /// <summary>
-    /// Helper method to get the decoded length of base64 data for debugger display.
-    /// </summary>
-    private protected static string GetBase64LengthDisplay(string base64Data)
-    {
-        try
-        {
-#if NET
-            if (System.Buffers.Text.Base64.IsValid(System.Text.Encoding.UTF8.GetBytes(base64Data), out int decodedLength))
-            {
-                return $"{decodedLength} bytes";
-            }
-            return "invalid base64";
-#else
-            byte[] decoded = Convert.FromBase64String(base64Data);
-            return $"{decoded.Length} bytes";
-#endif
-        }
-        catch
-        {
-            return "invalid base64";
-        }
-    }
-
     /// <summary>
     /// When overridden in a derived class, gets the type of content.
     /// </summary>
@@ -380,7 +356,7 @@ public override void Write(Utf8JsonWriter writer, ContentBlock value, JsonSerial
 }
 
 /// <summary>Represents text provided to or from an LLM.</summary>
-[DebuggerDisplay("Text = \\\"{Text}\\\"")]
+[DebuggerDisplay("Text = \"{Text}\"")]
 public sealed class TextContentBlock : ContentBlock
 {
     /// <inheritdoc/>
@@ -419,7 +395,7 @@ public sealed class ImageContentBlock : ContentBlock
     public required string MimeType { get; set; }
 
     [DebuggerBrowsable(DebuggerBrowsableState.Never)]
-    private string DebuggerDisplay => $"MimeType = {MimeType}, Length = {GetBase64LengthDisplay(Data)}";
+    private string DebuggerDisplay => $"MimeType = {MimeType}, Length = {DebuggerDisplayHelper.GetBase64LengthDisplay(Data)}";
 }
 
 /// <summary>Represents audio provided to or from an LLM.</summary>
@@ -445,7 +421,7 @@ public sealed class AudioContentBlock : ContentBlock
     public required string MimeType { get; set; }
 
     [DebuggerBrowsable(DebuggerBrowsableState.Never)]
-    private string DebuggerDisplay => $"MimeType = {MimeType}, Length = {GetBase64LengthDisplay(Data)}";
+    private string DebuggerDisplay => $"MimeType = {MimeType}, Length = {DebuggerDisplayHelper.GetBase64LengthDisplay(Data)}";
 }
 
 /// <summary>Represents the contents of a resource, embedded into a prompt or tool call result.</summary>
@@ -479,7 +455,7 @@ public sealed class EmbeddedResourceBlock : ContentBlock
 /// <remarks>
 /// Resource links returned by tools are not guaranteed to appear in the results of `resources/list` requests.
 /// </remarks>
-[DebuggerDisplay("Name = {Name}, Uri = \\\"{Uri}\\\"")]
+[DebuggerDisplay("Name = {Name}, Uri = \"{Uri}\"")]
 public sealed class ResourceLinkBlock : ContentBlock
 {
     /// <inheritdoc/>

src/ModelContextProtocol.Core/Protocol/DebuggerDisplayHelper.cs

@@ -0,0 +1,33 @@
+using System;
+
+namespace ModelContextProtocol.Protocol;
+
+/// <summary>
+/// Internal helper methods for DebuggerDisplay implementations.
+/// </summary>
+internal static class DebuggerDisplayHelper
+{
+    /// <summary>
+    /// Gets the decoded length of base64 data for debugger display.
+    /// </summary>
+    internal static string GetBase64LengthDisplay(string base64Data)
+    {
+#if NET
+        if (System.Buffers.Text.Base64.IsValid(System.Text.Encoding.UTF8.GetBytes(base64Data), out int decodedLength))
+        {
+            return $"{decodedLength} bytes";
+        }
+        return "invalid base64";
+#else
+        try
+        {
+            byte[] decoded = Convert.FromBase64String(base64Data);
+            return $"{decoded.Length} bytes";
+        }
+        catch
+        {
+            return "invalid base64";
+        }
+#endif
+    }
+}

src/ModelContextProtocol.Core/Protocol/TextResourceContents.cs

@@ -20,7 +20,7 @@ namespace ModelContextProtocol.Protocol;
 /// See the <see href="https://github.com/modelcontextprotocol/specification/blob/main/schema/">schema</see> for more details.
 /// </para>
 /// </remarks>
-[DebuggerDisplay("Uri = \\\"{Uri}\\\", Text = \\\"{Text}\\\"")]
+[DebuggerDisplay("Uri = \"{Uri}\", Text = \"{Text}\"")]
 public sealed class TextResourceContents : ResourceContents
 {
     /// <summary>