The predefined reference types are object and string. The type object is the ultimate base type of all other types. The type string is used to represent Unicode string values. Values of type string are immutable.

The predefined value types include signed and unsigned integral types, floating-point types, and the types bool, char, and decimal. The signed integral types are sbyte, short, int, and long; the unsigned integral types are byte, ushort, uint, and ulong; and the floating-point types are float and double.

The bool type is used to represent Boolean values: values that are either true or false. The inclusion of bool makes it easier to write self-documenting code, and also helps eliminate the all-too-common C++ coding error in which a developer mistakenly uses "=" when "==" should have been used. In C#, the example

The char type is used to represent Unicode characters. A variable of type char represents a single 16-bit Unicode character. Character type; a char value is a Unicode character char val = 'h';

The decimal type is appropriate for calculations in which rounding errors caused by floating point representations are unacceptable. Common examples include financial calculations such as tax computations and currency conversions. The decimal type provides 28 significant digits.

Each of the predefined types is shorthand for a system-provided type. For example, the keyword int refers to the struct System.Int32. As a matter of style, use of the keyword is favored over use of the complete system type name.

Two expressions of type int are considered equal if they represent the same integer value. Two expressions of type object are considered equal if both refer to the same object, or if both are null. Two expressions of type string are considered equal if the string instances have identical lengths and identical characters in each character position, or if both are null.

The following table shows some of the differences between values types and reference types.