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Compiler Error CS0075

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To cast a negative value, you must enclose the value in parentheses

If you are casting using a keyword that identifies a predefined type, then you do not need parentheses. Otherwise, you must put the parentheses because (x) –y will not be considered a cast expression. From the C# Specification, Section 7.6.6:

From the disambiguation rule it follows that, if x and y are identifiers, (x)y, (x)(y), and (x)(-y) are cast-expressions, but (x)-y is not, even if x identifies a type. However, if x is a keyword that identifies a predefined type (such as int), then all four forms are cast-expressions (because such a keyword could not possibly be an expression by itself).

The following code generates CS0075:

// CS0075  
namespace MyNamespace  
{  
    enum MyEnum { }  
    public class MyClass  
    {  
        public static void Main()  
        {  
            // To fix the error, place the negative  
            // values below in parentheses  
            int i = (System.Int32) - 4; //CS0075  
            MyEnum e = (MyEnum) - 1;    //CS0075  
            System.Console.WriteLine(i); //to avoid warning  
            System.Console.WriteLine(e); //to avoid warning  
        }  
    }  
}

See also