A better way than making it static (you'll run into all kinds of problems with this approach, especially if you want to use the designer after making those suggested changes) is to either pass a reference to the ListView to the form you open, or make a public property that gets the ListView on the first form and pass a reference to the first form into the second form (probably better if you ever want to do similar things in the future), or - finally - provide a way to get the data from the second form inside the first form and then have your first form add the data to your ListView. The latter method is probably best. This allows you to use that form in different places and different ways. Once ShowDialog returns, you can grab that data (in a collection, list, array, a single property or properties, or whatever) and use it however you want.
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