CA2133: Delegates must bind to methods with consistent transparency


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The latest version of this topic can be found at CA2133: Delegates must bind to methods with consistent transparency.

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System_CAPS_ICON_note.jpg Note

This warning is only applied to code that is running the CoreCLR (the version of the CLR that is specific to Silverlight Web applications).

This warning fires on a method that binds a delegate that is marked with the SecurityCriticalAttribute to a method that is transparent or that is marked with the SecuritySafeCriticalAttribute. The warning also fires a method that binds a delegate that is transparent or safe-critical to a critical method.

Delegate types and the methods that they bind to must have consistent transparency. Transparent and safe-critical delegates may only bind to other transparent or safe-critical methods. Similarly, critical delegates may only bind to critical methods. These binding rules ensure that the only code that can invoke a method via a delegate could have also invoked the same method directly. For example, binding rules prevent transparent code from calling critical code directly via a transparent delegate.

To fix a violation of this warning, change the transparency of the delegate or of the method that it binds so that the transparency of the two are equivalent.

Do not suppress a warning from this rule.


using System;
using System.Security;

namespace TransparencyWarningsDemo

    public delegate void TransparentDelegate();

    public delegate void CriticalDelegate();

    public class TransparentType
        void DelegateBinder()
            // CA2133 violation - binding a transparent delegate to a critical method
            TransparentDelegate td = new TransparentDelegate(CriticalTarget);

            // CA2133 violation - binding a critical delegate to a transparent method
            CriticalDelegate cd = new CriticalDelegate(TransparentTarget);

        void CriticalTarget() { }

        void TransparentTarget() { }