. Net (C #) platform call: Sending of classes and struct

Using getcursorpos as an example, it returns the position of the current mouse pointer on the screen (with a point structure ).

For definitions of getcursorpos and point, refer to msdn:

Http://msdn.microsoft.com/en-us/library/ms648390 (V = vs.85). aspx

Http://msdn.microsoft.com/en-us/library/dd162805 (V = vs.85). aspx

 

First, use a custom C # struct to call getcursorpos. Everything looks simple.

Define a memory continuous struct point, and use the out parameter in the platform call life, because getcursorpos requires a point pointer! In execution, first declare a point variable (which involves space allocation), then call getcursorpos, and finally output the structure, correct!

Static void main ()

{

Point P;

Getcursorpos (Out P );

Console. writeline (P );

}

 

[Structlayout (layoutkind. Sequential)]

Struct point

{

Public int X, Y;

Public override string tostring ()

{

Return string. Format ("({0}, {1})", x, y );

}

}

 

[Dllimport ("user32.dll")]

Static extern void getcursorpos (out point P );

 

Next let's take a look at using a point class (rather than a struct) to implement the above functions. First, the out parameter is not required in the life of the platform call, because the class is a reference type and itself is a pointer!

Next, it is important to use the outattribute attribute to indicate the point parameter, because the default value is inattribute (if there is no ref/out ).

Finally, it is the space allocation. The reference type needs to be allocated with new.

Once everything above is set, the call can be successful. Code:

Static void main ()

{

Point P = new point ();

Getcursorpos (P );

Console. writeline (P );

}

 

[Structlayout (layoutkind. Sequential)]

Class Point

{

Public int X, Y;

Public override string tostring ()

{

Return string. Format ("({0}, {1})", x, y );

}

}

 

[Dllimport ("user32.dll")]

Static extern void getcursorpos ([out] point P );

 

Note that the structlayout feature can also modify the class!