Use less memory when generating a GuidUdi (#13090)

* Use less memory when generating a GuidUdi

* PR feedback

Co-authored-by: Sebastiaan Janssen <sebastiaan@umbraco.com>

src/Umbraco.Core/Constants-Conventions.cs

@@ -348,5 +348,10 @@ public static partial class Constants
 
             // TODO: return a list of built in types so we can use that to prevent deletion in the uI
         }
+
+        public static class Udi
+        {
+            public const string Prefix = "umb://";
+        }
     }
 }

src/Umbraco.Core/GuidUdi.cs

@@ -1,4 +1,5 @@
 using System.ComponentModel;
+using Umbraco.Extensions;
 
 namespace Umbraco.Cms.Core;
 
@@ -14,7 +15,7 @@ public class GuidUdi : Udi
     /// <param name="entityType">The entity type part of the udi.</param>
     /// <param name="guid">The guid part of the udi.</param>
     public GuidUdi(string entityType, Guid guid)
-        : base(entityType, "umb://" + entityType + "/" + guid.ToString("N")) =>
+        : base(entityType, CreateStringValue(entityType, guid)) =>
         Guid = guid;
 
     /// <summary>
@@ -57,4 +58,19 @@ public class GuidUdi : Udi
         EnsureNotRoot();
         return this;
     }
+
+    private static string CreateStringValue(ReadOnlySpan<char> entityType, Guid guid)
+    {
+        var startUdiLength = Constants.Conventions.Udi.Prefix.Length;
+        var outputSize = entityType.Length + startUdiLength + 32 + 1; //Based on the format umb://entityType/guid (32 = Guid N format, 1 = / between entityType and guid)
+        Span<char> output = stackalloc char[outputSize];
+
+        //Add all the values of the format to the output
+        Constants.Conventions.Udi.Prefix.CopyTo(output[..startUdiLength]);
+        entityType.CopyTo(output.Slice(startUdiLength, entityType.Length));
+        output[startUdiLength + entityType.Length] = '/';
+        guid.TryFormat(output.Slice(outputSize - 32, 32), out _, "N");
+
+        return new string(output);
+    }
 }

src/Umbraco.Core/StringUdi.cs

@@ -14,7 +14,7 @@ public class StringUdi : Udi
     /// <param name="entityType">The entity type part of the udi.</param>
     /// <param name="id">The string id part of the udi.</param>
     public StringUdi(string entityType, string id)
-        : base(entityType, "umb://" + entityType + "/" + EscapeUriString(id)) =>
+        : base(entityType, Constants.Conventions.Udi.Prefix + entityType + "/" + EscapeUriString(id)) =>
         Id = id;
 
     /// <summary>