Ensure LazyCompressedString doesn't decompress when debugging

src/Umbraco.Web/PublishedCache/NuCache/DataSource/LazyCompressedString.cs

@@ -1,5 +1,6 @@
 using K4os.Compression.LZ4;
 using System;
+using System.Diagnostics;
 using System.Text;
 using Umbraco.Core.Exceptions;
 
@@ -8,6 +9,7 @@ namespace Umbraco.Web.PublishedCache.NuCache.DataSource
     /// <summary>
     /// Lazily decompresses a LZ4 Pickler compressed UTF8 string
     /// </summary>
+    [DebuggerDisplay("{Display}")]
     internal struct LazyCompressedString
     {
         private byte[] _bytes;
@@ -22,29 +24,85 @@ namespace Umbraco.Web.PublishedCache.NuCache.DataSource
         {
             _locker = new object();
             _bytes = bytes;
-            _str = null;            
+            _str = null;
         }
 
         public byte[] GetBytes()
         {
             if (_bytes == null)
+            {
                 throw new InvalidOperationException("The bytes have already been expanded");
+            }
+
             return _bytes;
         }
 
-        public override string ToString()
+        /// <summary>
+        /// Returns the decompressed string from the bytes. This methods can only be called once.
+        /// </summary>
+        /// <returns></returns>
+        /// <exception cref="InvalidOperationException">Throws if this is called more than once</exception>
+        public string DecompressString()
         {
-            if (_str != null) return _str;
+            if (_str != null)
+            {
+                return _str;
+            }
+
             lock (_locker)
             {
-                if (_str != null) return _str; // double check
-                if (_bytes == null) throw new PanicException("Bytes have already been cleared");
+                if (_str != null)
+                {
+                    // double check
+                    return _str;
+                }
+
+                if (_bytes == null)
+                {
+                    throw new InvalidOperationException("Bytes have already been cleared");
+                }
+
                 _str = Encoding.UTF8.GetString(LZ4Pickler.Unpickle(_bytes));
                 _bytes = null;
             }
             return _str;
         }
 
+        /// <summary>
+        /// Used to display debugging output since ToString() can only be called once
+        /// </summary>
+        private string Display
+        {
+            get
+            {
+                if (_str != null)
+                {
+                    return $"Decompressed: {_str}";
+                }
+
+                lock (_locker)
+                {
+                    if (_str != null)
+                    {
+                        // double check
+                        return $"Decompressed: {_str}";
+                    }
+
+                    if (_bytes == null)
+                    {
+                        // This shouldn't happen
+                        throw new PanicException("Bytes have already been cleared");
+                    }
+                    else
+                    {
+                        return $"Compressed Bytes: {_bytes.Length}";
+                    }
+                }
+            }
+        }
+
+        public override string ToString() => DecompressString();
+
         public static implicit operator string(LazyCompressedString l) => l.ToString();
     }