How to cast Expression> to Expression>

Question

I\'ve been searching but I can\'t find how to cast from the type

Expression>

to the type:

Exp         


        

Answer 1

The answers from Rob and Jon Skeet have one problem.

You get something like x => Convert(x.PropertyName), but often for instance for ASP.NET MVC you want an expression like this x => x.PropertyName

So Expression.Convert is "polluting" the expression for some cases.

Solution:

public static class LambdaExpressionExtensions
{
    public static Expression> ToUntypedPropertyExpression (this Expression> expression)
    {
        var memberName = ((MemberExpression)expression.Body).Member.Name;

        var param = Expression.Parameter(typeof(TInput));
        var field = Expression.Property(param, memberName);
        return Expression.Lambda>(field, param);
    }
}

Usage:

Expression> expression = ...;
Expression> expr = expression.ToUntypedPropertyExpression();