Question: I have a very generic extension method to show any type of list within a console:

```
public static void ShowList<T>(this IEnumerable<T> Values)
{
    foreach (T item in Values)
    {
        Console.WriteLine(item);
    }
}

```

Not when I have a `string` I can use this Method 

```
string text = "test";
text.ShowList();

```

But in case of `string` it doesn't make sense in my application. 

How can I exclude `string` from this method? I've read something about 

```
ShowList<T>(this IEnumerable<T> Values): Where != string //doesn't work

```

Answer: 
This feels like a bit of an odd requirement to start with, to be honest - if something should work for any sequence of characters, then it should work for a string, which *is* a sequence of characters.

If you really want to make it fail to compile, you could add an overload accepting `string` which is marked as obsolete:

```
[EditorBrowsable(EditorBrowsableState.Never)]
[Obsolete(IsError = true, Message = "A string is a sequence of characters, but is not intended to be shown as a list")]
public static void ShowList(this string text)
{
    throw new NotSupportedException();
}

```

Overload resolution will pick that method, and then it'll fail to compile. The `EditorBrowsable` attribute will *hopefully* remove this from Intellisense - but you'll have to see whether that actually works. (It may show the other overload still, even though that wouldn't be picked.)

Another option would be to implement `ShowList<T>` as if the string was a single-entry list:

```
// Specialization to avoid listing each character separately.
public static void ShowList(this string text) => new[] { text }.ShowList();

```

In other words, make it valid to call, but handle it more appropriately.
You can create another overload of `ShowList()` that is specific for `string` and mark it as `[Obsolete]`:

```
[Obsolete("Not intended for strings", true)]
public static void ShowList(this string val)
{
}

```

By passing `true` to the `IsError` parameter, the compiler will prevent you from using the method.

See [ObsoleteAttribute](https://msdn.microsoft.com/en-us/library/system.obsoleteattribute(v=vs.110).aspx)