How can I take an existing function and write it using Func<..> in C#?
I wrote this code:
public static bool MyMethod(int someid, params string[] types)
{...}
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How could I write that using Func?
public static Func < int, ?params?, bool > MyMethod = ???
The params
keyword is compiled to an ordinary parameter with the ParamArray
. You cannot apply an attribute to a generic parameter, so your question is impossible.
Note that you could still use a regular (non-params
) delegate:
Func<int, string[], bool> MyMethodDelegate = MyMethod;
In order to use the params keyword with a delegate, you'll need to make your own delegate type:
public delegate bool MyMethodDelegate(int someid, params string[] types);
You could even make it generic:
public delegate TResult ParamsFunc<T1, T2, TResult>(T1 arg1, params T2[] arg2);
Short answer, you can't, if you really want to preserve the params
functionality.
Otherwise, you could settle for:
Func<int, string[], bool> MyMethod = (id, types) => { ... }
bool result = MyMethod(id, types);
i'm afraid you couldn't do that.
http://msdn.microsoft.com/en-us/library/w5zay9db%28VS.71%29.aspx
I don't think there's a way to declare functions through Func... although you can just do:
public static bool MyMethod(int someid, params string[] types) {...}
public static Func < int,params string[], bool > MyFunc = MyMethod;
I think you want a Func declaration as such:
public static Func<int, string[], bool> MyMethod = ???
How about some helper methods like these?
public static TResult InvokeWithParams<T, TResult>
(this Func<T[], TResult> func, params T[] args) {
return func(args);
}
public static TResult InvokeWithParams<T1, T2, TResult>
(this Func<T1, T2[], TResult> func, T1 arg1, params T2[] args2) {
return func(arg1, args2);
}
Obviously, you could implement this for additional generic overloads of Func
(as well as Action
, for that matter).
Usage:
void TestInvokeWithParams() {
Func<string[], bool> f = WriteLines;
int result1 = f.InvokeWithParams("abc", "def", "ghi"); // returns 3
int result2 = f.InvokeWithParams(null); // returns 0
}
int WriteLines(params string[] lines) {
if (lines == null)
return 0;
foreach (string line in lines)
Console.WriteLine(line);
return lines.Length;
}
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