For an operation of the form x
+
y
, binary operator overload resolution (§7.2.4) is applied to select a specific operator implementation. The operands are converted to the parameter types of the selected operator, and the type of the result is the return type of the operator.
The predefined addition operators are listed below. For numeric and enumeration types, the predefined addition operators compute the sum of the two operands. When one or both operands are of type string, the predefined addition operators concatenate the string representation of the operands.
int operator +(int x, int y); uint operator +(uint x, uint y); long operator +(long x, long y); ulong operator +(ulong x, ulong y);
In a checked
context, if the sum is outside the range of the result type, an OverflowException
is thrown. In an unchecked
context, overflows are not reported and any significant high-order bits of the result are discarded.
float operator +(float x, float y); double operator +(double x, double y);
The sum is computed according to the rules of IEEE 754 arithmetic. The following table lists the results of all possible combinations of nonzero finite values, zeros, infinities, and NaNs. In the table, x
and y
are nonzero finite values, and z
is the result of x
+
y
. If x
and y
have the same magnitude but opposite signs, z
is positive zero. If x
+
y
is too large to represent in the destination type, z
is an infinity with the same sign as x
+
y
. If x
+
y
is too small to represent in the destination type, z
is a zero with the same sign as x
+
y
.
y |
+0 |
0 |
+8 |
8 |
NaN |
|
x |
z |
x |
x |
+8 |
8 |
NaN |
+0 |
y |
+0 |
+0 |
+8 |
8 |
NaN |
0 |
y |
+0 |
0 |
+8 |
8 |
NaN |
+8 |
+8 |
+8 |
+8 |
+8 |
NaN |
NaN |
8 |
8 |
8 |
8 |
NaN |
8 |
NaN |
NaN |
NaN |
NaN |
NaN |
NaN |
NaN |
NaN |
decimal operator +(decimal x, decimal y);
If the resulting value is too large to represent in the decimal
format, an OverflowException
is thrown. If the result value is too small to represent in the decimal
format, the result is zero.
E
is the enum type, and U
is the underlying type of E
:E operator +(E x, U y); E operator +(U x, E y);
The operators are evaluated exactly as (E)((U)x
+
(U)y)
.
string operator +(string x, string y); string operator +(string x, object y); string operator +(object x, string y);
The binary +
operator performs string concatenation when one or both operands are of type string
. If an operand of string concatenation is null
, an empty string is substituted. Otherwise, any non-string argument is converted to its string representation by invoking the virtual ToString()
method inherited from type object
. If ToString()
returns null
, an empty string is substituted.
The result of the string concatenation operator is a string that consists of the characters of the left operand followed by the characters of the right operand. The string concatenation operator never returns a null
value. An OutOfMemoryException
may be thrown if there is not enough memory available to allocate the resulting string.
D
is the delegate type:D operator +(D x, D y);