Array of structures CLI

public value struct ListOfWindows
{
 HWND hWindow;
 int winID;
 String^ capName;
};

thats my structure now i have created an array of them:

array<ListOfWindows ^> ^ MyArray =  gcnew array<ListOfWindows ^>(5);

now t开发者_JAVA技巧o test if that works i made a simple function:

void AddStruct( )
{
  HWND temp = ::FindWindow( NULL, "Test" );
  if( temp == NULL ) return;
  MyArray[0]->hWindow = temp; // debug time error..

  return;
}

ERROR: An unhandled exception of type 'System.NullReferenceException' occurred in Window.exe

Additional information: Object reference not set to an instance of an object.

dont know what to do.. kinda new to CLI so if you can help please do.. Thanks.

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Well, you have an array of references to objects but I don't see any code that actually puts an object into any of them. Before accessing MyArray[0] you might want to put an object into the array at position 0.

I would change ListOfWindows to be a ref class - in your context it doesn't make much sense to use it as a value class - and then you can add an object to the array like this:

MyArray[0] = gcnew ListOfWindows;

(Untested but that's more or less how it should work). Once you've actually added that object you can then interact with it.

---

First you're creating an array of references not an array of values, so as @timo-geusch says you need to create those objects after creating your array of references.

However you could also create an array of values like this.

array<ListOfWindows>^ MyArray =  gcnew array<ListOfWindows>(5);

Then you'd access those values with the . operator instead of -> operator, like this.

void AddStruct( )
{
    HWND temp = ::FindWindow( NULL, "Test" );
    if( temp == NULL ) return;
    MyArray[0].hWindow = temp; // << here you access the value type, not the reference
    return;
}

Hope that helps