如何在表达式树c＃中使用隐式转换？

Question

I have simplified program, which uses expressions:

public class Program
{
    public static IEnumerable<char> foo1()
    {
        //  For some reason I cannot change result type
        return new char[] { 's', '1' };
    }

    public static string foo2()
    {
        //  For some reason I cannot change result type
        return "s1";
    }

    static void Main()
    {
        Expression cond = Expression.Condition(Expression.Constant(true), 
            Expression.Call(typeof(Program).GetMethod("foo1")),
            Expression.Call(typeof(Program).GetMethod("foo2")));
    }
}

During execution I have following error

Argument types do not match.

As I understood c# does not use implicit type casting. How can I solve this problem?

Answer 1

When building expressions it's not going to add in implicit conversions for you. You need to specifically indicate that you want to apply the conversion operator(s) using Expression.Convert .

Expression cond = Expression.Condition(Expression.Constant(true),
    Expression.Call(typeof(Program).GetMethod("foo1")),
    Expression.Convert(Expression.Call(typeof(Program).GetMethod("foo2")), typeof(IEnumerable<char>)));