Explicitly tell compiler to stop optimization and keep an unused variable in C#

Question

I have a method that return someCalssObject.SomeProperty. In the program, the value of someCalssObject.SomeProperty is lazily initialized (i.e. the data is not computed until it is used).

Due to some architectural issue in the program (not in my hand to fix it), if I return this lazily initialized property someCalssObject.SomeProperty, some of the values gets already disposed by the time program really needs to use the data present inside someCalssObject.SomeProperty. And hence, the program generates unexpected outputs.

To resolve the use, I have introduced a dummy variable (dummyVariable) which forces the computation of the data for the property someCalssObject.SomeProperty.

protected override void SomeMethod()
{
    //Some Code
            
    //MUST HAVE THIS LINE (even though the CANNOT be used anywhere)
    var dummyVariable = someCalssObject.SomeProperty.GetValues<float>(); //This line forces the computation of some Lazily Initialized data     
                        
    // Some more code
    
    return someCalssObject.SomeProperty;
}

With the above approach of introducing a dummy variable, the program is working fine (both in debug and release mode). But I am afraid that the compiler may/will remove the line computing dummy variable (dummyVariable ) as optimization since the variable is not used anywhere.

QUESTION: How can I tell the compiler to keep the line that is computing the dummy variable without making any change in the compilation settings? Will declaring the unused variable as static volatile a robust solution?

Answer 1

If you want to make sure the value of dummyVariable is not GC'ed until the function ends, you can add GC.KeepAlive(dummyVariable) at the end of your function (you may need to create a variable for your return value, too). The method does nothing, but ensures a reference to the value used as argument exists until it is called.

So that would be:

protected override void SomeMethod()
{
    //Some Code
            
    //MUST HAVE THIS LINE (even though the CANNOT be used anywhere)
    var dummyVariable = someCalssObject.SomeProperty.GetValues<float>(); //This line forces the computation of some Lazily Initialized data     
                        
    // Some more code
    
    var ret = someCalssObject.SomeProperty;
    GC.KeepAlive(dummyVariable);
    return ret;
}