Passing a static var by reference

Esteban Francisco

I am having trouble updating a static variable by reference. I have a parent class passing a static variable into new class constructor by reference. The parent class is the primary executable. The new class is in a separate DLL. I can easily change the value of the static variable in the new class's constructor and it's reflected in the parent. Unfortunately, I cannot update this static variable from another method in the new class.

The flow of my program is something like the following:

[code]
namespace Somewhere
{
public partial class TestReporter : Form
{
    private TestForm tForm;
    public static bool TestInProgress = false;

    void someMethod()
    {
      tForm = new TestForm(ref TestInProgress);
    }
}
}
[/code]

[code]
namespace OverTheRainbow
{
public class Test
{
    public bool RainbowProgress = false;

    public Test(ref bool prog)
    {
      RainbowProgress = prog;
    }

    void someOtherMethod()
    {
      RainbowProgress = true;
    }
}
}
[/code]

So you see, I was hoping that calling someOtherMethod() in the TestForm class would update the parent's TestInProgress value. Unfortunately, I was wrong. Now, I am a C/C++ guy and my first though to solve this is pointers. I even tried to use pointers with C#, but with all the unsafe keywords and having to tell the compiler to use unsafe code, it just seemed way inappropriate. There has to be a way to update that boolean value in the parent class using something more natural to C#.

Can anyone help with this? Thank you so much!

3 Replies

Know the answer? Post it — somebody with the same question will find it here.

Vulpes15y ago
Accepted answer
It's just occurred to me that if someOtherMethod is in a dll, then it won't necessarily know what classes are in the client exe.

In that case, if you'd rather avoid pointers and unsafe code, then one way of doing what you want would be to use a bool array with one element rather than a scalar bool variable. As an array is a reference type, a change made to the value of its only element in the dll will be automatically reflected in the exe because it's the same object and not a copy. The code would then be:

namespace Somewhere
{
public partial class TestReporter : Form
{
private TestForm tForm;
public static bool[] TestInProgress = new bool[1]; // element is false by default

void someMethod()
{
tForm = new TestForm(TestInProgress); // ref no longer needed as reference type anyway
}
}
}

namespace OverTheRainbow
{
public class Test
{
public bool[] RainbowProgress = new bool[1]; // element is false by default

public Test(bool[] prog)
{
RainbowProgress = prog;
}

void someOtherMethod()
{
RainbowProgress[0] = true; // change value of only element
}
}
}
Esteban Francisco15y ago
Vulpes, thank you very much for the tip. For some reason, using a single element array never crossed my mind. It isn't the prettiest solution, but it works well until I can think of something better. I am sure I will get lambasted at my next code review, but it's going to stay this way until they think of a better idea. lol.

I am glad you noticed that this was a DLL communicating information to an executable. I was afraid I wasn't clear. The usage of "unsafe" pointers is pretty ridiculous in C#, so I am glad to have avoided it. In the end, I can now prevent a user from reviewing test data in the parent executable before the test is complete in the DLL.

As for the namespaces... yeah. Not sure where my head was. *grin* Thanks again.

P.S. Since the client and the dll use a shared common library, I created something like the following to make usage prettier. Now they can both access the object and everyone can live happily ever after.

public class RainbowProgress
{
    private static bool[] TestInProgress = new bool[1];

    public static bool Status
    {
      get
      {
        return TestInProgress[0];
      }
      set
      {
        TestInProgress[0] = value;
      }
    }
}
Vulpes15y ago
As TestInProgress is a public static field of the Somewhere.TestReporter class, you can update it from OverTheRainbow.Test.someOtherMethod() as follows:

void someOtherMethod()
{
RainbowProgress = true;
Somewhere.TestReporter.TestInProgress = true;
}

As bool is a value type, changing RainbowProgress will have no effect on TestInProgress.

BTW, some nice names for your namespaces ;)