Rider incorrectly reports Syntax error for valid XML doc constructor cref references (#ctor)

Created May 21, 2026 15:13

Rider marks the XML doc comment itself as invalid.

public sealed class Class1
{
   public Class1() { }
}

internal static class ClassDocs
{
   /// <summary>
   /// Dispose a Instance of <see cref="Class1"/>.
   /// </summary>
   /// <seealso cref="Class1.#ctor"/>
   public static extern void Dispose();
}

Rider highlights:
#ctor
with:
Syntax error

The same happens with qualified members:
/// <seealso cref="M:Class1.#ctor"/>

Rider should accept constructor references using:
#ctor
#ctor(System.Int32,System.String)

1 comment

Dmitry Kazantsev

Created May 26, 2026 14:48

Hello Cig,

This is a valid warning, not a false-positive.

The goal of writing xml documentation is to generate xml documentation. Once you enable “<GenerateDocumentationFile>true</GenerateDocumentationFile>” in .csproj file, you will start getting compiler warnings like this:

1>{path}\Sample.cs(18,24,18,31): warning CS1584: XML comment has syntactically incorrect cref attribute 'Class1.#ctor'
1>{path}\Sample.cs(18,31,18,32): warning CS1658: Identifier expected. See also error CS1001.
1>{path}\Sample.cs(18,31,18,31): warning CS1658: Unexpected character '#'. See also error CS1056.

The syntax you provided M:Class1.#ctor is the resulting string ID produced in the xml documentation file output, but you shouldn't use this for documenting purpose ‘on frontend’ (when writing .cs). Such a syntax isn't valid.

I wasn't able to find exactly statement prohibiting that, but I assume we can trust compiler here. And I found this:

The cref attribute can be attached to any tag to provide a reference to a code element. The documentation generator must verify that this code element exists. If the verification fails, the documentation generator issues a warning. When looking for a name described in a cref attribute, the documentation generator must respect namespace visibility according to using statements appearing within the source code.oi

And if you add “<TreatWarningsAsErrors>true</TreatWarningsAsErrors>” the project will fail to build:

Hope that helps. Have a nice day!

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