C #4.0 New Feature 2: named and optional parameters (1)

This feature is relatively simple, and we will continue to talk about it for a long time, but only focus on it. In the following demo, we often use overload functions to handle problems:

Code
1 Public   Void Process ( Int P1, Float P2, String P3)
2 {
3 // Todo
4 }
5
6 Public   Void Process ( Int P1, Float P2)
7 {
8 Process (P1, P2, " Fanweixiao " );
9 }
10
11 Public   Void Process ( Int P1)
12 {
13 Process (P1, 0f );
14 }

 

In the era of C #4.0, two new functions are provided, named parameters and optional parameters ). They are two completely independent concepts, but they are often used together. The rewritten function is:

Code
1 Public   Int Nbprocess ( Int P1 = 0 , Float P2 = 0f, String P3 = " Fanweixiao " )
2 {
3 // Todo
4 }

 

In this way, we can use nbprocess (10) to call this function, which is equivalent to calling nbprocess (10, 0f, "fanweixiao.

To save the second parameter, we can call: nbprocess (10,P3: "Fanweixiao "). You can also write it as nbprocess (P1: 10, P3: "fanweixiao "). You can even change the Parameter order nbprocess (P3: "Fanweixiao ",P1: 10.

This can also be used for constructors and indexer.

For overload of such parameters, the logic is also very simple:Similarity principle. (Applicable)

From the perspective of parameter 5, M (string, INT) is excluded first, because it requires the first parameter to be of the string type. M (INT, string) is acceptable because string is an optional parameter. It and M (INT) are better than m (object), and the object is the "source of all evil, 5 and INT are much more friendly. In the end, M (INT) is the best.

The location and number of parameters of different types in the constructor are the key to determining their differentiation. This feature of C #4.0 puts the parameter name in the rule, the name of the parameter must be more serious later :). In fact, the above functions are supported in dynamic languages like python, and there is a cool "* parameter ":

Code
1 Def Stepper (what, = 1 ):
2 What + = By
3 Return What
4
5 Def Average (first, * Rest ):
6 Sum = First
7 ForValueInRest: Sum+ = Value
8 Result =   1.0   * Sum / (LEN (rest) +   1 )
9 Return Result

Of course, we can also use the param keyword to do this, but it is not as cool as Python, but it is enough :)