You can store the value in public static variable. Example:
public class MyGlobalValue
{
public static string MyGlobalString = "Hello";
public static int MyGlobalInt = 1234;
}
You can access it anywhere in your application like this:
MyGlobalValue.MyGlobalString += ", nice to meet you.";
MesssageBox.Show(MyGlobalValue.MyGlobalString);
int a = MyGlobalValue.MyGlobalInt + 1;
MessageBox.Show("MyGlobalValue.MyGlobalInt + 1 = " + a);