+ Operator (C# Reference)
The + operator can function as either a unary or a binary operator.
Remarks
Unary + operators are predefined for all numeric types. The result of a unary + operation on a numeric type is just the value of the operand.
Binary + operators are predefined for numeric and string types. For numeric types, + computes the sum of its two operands. When one or both operands are of type string, + concatenates the string representations of the operands.
Delegate types also provide a binary + operator, which performs delegate concatenation.
User-defined types can overload the unary + and binary + operators. Operations on integral types are generally allowed on enumeration. For more information, see operator (C# Reference).
Example
class Plus
{
static void Main()
{
Console.WriteLine(+5); // unary plus
Console.WriteLine(5 + 5); // addition
Console.WriteLine(5 + .5); // addition
Console.WriteLine("5" + "5"); // string concatenation
Console.WriteLine(5.0 + "5"); // string concatenation
// note automatic conversion from double to string
}
}
/*
Output:
5
10
5.5
55
55
*/
C# Language Specification
For more information, see the C# Language Specification. The language specification is the definitive source for C# syntax and usage.