CODEWITHSUNDEEP
c#.netgenericsreflection
Alex Zhukovskiy
Alex Zhukovskiy

Reputation: 10015

GetMethod overload returns null

I want to get a method from specific interface, but it can be in multiple interfaces. I write this code:

private static Expression<Func<T, T, int>> CreateCompareTo<TProperty>(MemberExpression expression, Expression<Func<T, T, int>> result) where TProperty : IComparable<TProperty>, IComparable
{
    var methodInfo = typeof(TProperty).GetMethod("CompareTo", new[] { typeof(IComparable<TProperty>), typeof(IComparable) });
    ...

MSDN

An array of Type objects representing the number, order, and type of the parameters for the method to get.

So I expect that it will search method through IComparable<T>, and, if didn't found, will search it in non-generic IComparable. But it doesn't. Well, now I rewrite it:

private static Expression<Func<T, T, int>> CreateCompareTo<TProperty>(MemberExpression expression, Expression<Func<T, T, int>> result) where TProperty : IComparable<TProperty>, IComparable
{
    Type t = typeof(TProperty);
    var methodInfo = t.GetMethod("CompareTo", new[] { typeof(IComparable<TProperty>) }) ?? t.GetMethod("CompareTo", new[] { typeof(IComparable) });
    ...

And now it works.

Why first option is not working?

Upvotes: 1

Views: 268

Answers (1)

CodeCaster
CodeCaster

Reputation: 151588

GetMethod("CompareTo", new[] { typeof(IComparable<TProperty>), typeof(IComparable)})

So I expect that it will search method through IComparable, and, if didn't found, will search it in non-generic IComparable

No, it looks for a method with the signature CompareTo(IComparable<TProperty>, IComparable).

This is also in the Type.GetMethod() documentation:

Searches for the specified public method whose parameters match the specified argument types.

Upvotes: 4

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