Compiler Error CS1731

  • Article

Cannot convert 'expression' to delegate because some of the return types in the block are not implicitly convertible to the delegate return type.

This error is generated when a lambda expression or anonymous method has a return type that is not compatible with the delegate's return type.

To correct this error

  • Change the return type of either the delegate or the expression.

Example

The following code generates CS1731:

class CS1731
{
    delegate double D();
    D d = () => { return "Who knows the real sword of Gryffindor?"; };
}