What is a method group in C#?

Andrei_Rinea_1796 0
Viewed 193295

I have often encountered an error such as "cannot convert from 'method group' to 'string'" in cases like: 

var list = new List<string>();
// ... snip
list.Add(someObject.ToString);

of course there was a typo in the last line because I forgot the invocation parentheses after ToString. The correct form would be:

var list = new List<string>();
// ... snip
list.Add(someObject.ToString()); // <- notice the parentheses

However I came to wonder what is a method group. Google isn't much of a help nor MSDN.

method-group .net c#
5 Answers

A method group is the name for a set of methods (that might be just one) - i.e. in theory the ToString method may have multiple overloads (plus any extension methods): ToString(), ToString(string format), etc - hence ToString by itself is a "method group".

It can usually convert a method group to a (typed) delegate by using overload resolution - but not to a string etc; it doesn't make sense.

Once you add parentheses, again; overload resolution kicks in and you have unambiguously identified a method call.

Marc_Gravell_233540

The first result in your MSDN search said:

The method group identifies the one method to invoke or the set of overloaded methods from which to choose a specific method to invoke

my understanding is that basically because when you just write someInteger.ToString, it may refer to:

Int32.ToString(IFormatProvider)

or it can refer to:

Int32.ToString()

so it is called a method group.

user_892990

The ToString function has many overloads - the method group would be the group consisting of all the different overloads for that function.

1800_INFORMATION_31460
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