Function members are members that contain executable statements. Function members are always members of types and cannot be members of namespaces. C# defines the following five categories of function members:
The statements contained in function members are executed through function member invocations. The actual syntax for writing a function member invocation depends on the particular function member category. However, all function member invocations are expressions, allow arguments to be passed to the function member, and allow the function member to compute and return a result.
The argument list (§7.4.1) of a function member invocation provides actual values or variable references for the parameters of the function member.
Invocations of constructors, methods, indexers, and operators employ overload resolution to determine which of a candidate set of function members to invoke. This process is described in §7.4.2.
Once a particular function member has been identified at compile-time, possibly through overload resolution, the actual run-time process of invoking the function member is described in §7.4.3.
The following table summarizes the processing that takes place in constructs involving the five categories of function members. In the table, e
, x
, y
, and value
indicate expressions classified as variables or values, T
indicates an expression classified as a type, F
is the simple name of a method, and P
is the simple name of a property.
Construct | Example | Description |
Constructor invocation | new T(x, y) |
Overload resolution is applied to select the best constructor in the class or struct T . The constructor is invoked with the argument list (x, y) . |
Method invocation | F(x, y) |
Overload resolution is applied to select the best method F in the containing class or struct. The method is invoked with the argument list (x, y) . If the method is not static , the instance expression is this . |
T.F(x, y) |
Overload resolution is applied to select the best method F in the class or struct T . An error occurs if the method is not static . The method is invoked with the argument list (x, y) . |
|
e.F(x, y) |
Overload resolution is applied to select the best method F in the class, struct, or interface given by the type of e . An error occurs if the method is static . The method is invoked with the instance expression e and the argument list (x, y) . |
|
Property access | P |
The get accessor of the property P in the containing class or struct is invoked. An error occurs if P is write-only. If P is not static , the instance expression is this . |
P = value |
The set accessor of the property P in the containing class or struct is invoked with the argument list (value) . An error occurs if P is read-only. If P is not static , the instance expression is this . |
|
T.P |
The get accessor of the property P in the class or struct T is invoked. An error occurs if P is not static or if P is write-only. |
|
T.P = value |
The set accessor of the property P in the class or struct T is invoked with the argument list (value) . An error occurs if P is not static or if P is read-only. |
|
e.P |
The get accessor of the property P in the class, struct, or interface given by the type of e is invoked with the instance expression e . An error occurs if P is static or if P is write-only. |
|
e.P = value |
The set accessor of the property P in the class, struct, or interface given by the type of e is invoked with the instance expression e and the argument list (value) . An error occurs if P is static or if P is read-only. |
|
Indexer access | e[x, y] |
Overload resolution is applied to select the best indexer in the class, struct, or interface given by the type of e. The get accessor of the indexer is invoked with the instance expression e and the argument list (x, y) . An error occurs if the indexer is write-only. |
e[x, y] = value |
Overload resolution is applied to select the best indexer in the class, struct, or interface given by the type of e . The set accessor of the indexer is invoked with the instance expression e and the argument list (x, y, value) . An error occurs if the indexer is read-only. |
|
Operator invocation | -x |
Overload resolution is applied to select the best unary operator in the class or struct given by the type of x . The selected operator is invoked with the argument list (x) . |
x + y |
Overload resolution is applied to select the best binary operator in the classes or structs given by the types of x and y. The selected operator is invoked with the argument list (x, y) . |