Awesome

Unity-Minimum-Window-Size

Set minimum window size for Windows build in Unity

Usage

int minWidth = 200;
int minHeight = 300;

MinimumWindowSize.Set(minWidth, minHeight);

Don't forget to .Reset() before quitting, otherwise application will quit with exception

public class Example : MonoBehaviour {

    private void OnApplicationQuit(){
        MinimumWindowSize.Reset();
    }
}