Compiler Error CS1900
Warning level must be in the range 0-4
The /warn compiler option can only take one of five possible values (0, 1, 2, 3, or 4). Any other value passed to /warn will result in CS1900.
The following sample generates CS1900:
// CS1900.cs
// compile with: /W:5
// CS1900 expected
class x
{
public static void Main()
{
}
}