How to use [DllImport("")] in C#?

Question

I found a lot of questions about it, but no one explains how I can use this.

I have this:

using System; using System.Collections.Generic; using System.Linq; using System.Runtime.InteropServices; using System.Windows.Forms; using Microsoft.FSharp.Linq.RuntimeHelpers; using System.Diagnostics; using System.Runtime.InteropServices; using System.IO;  public class WindowHandling {     public void ActivateTargetApplication(string processName, List<string> barcodesList)     {         [DllImport("User32.dll")]         public static extern int SetForegroundWindow(IntPtr point);         Process p = Process.Start("notepad++.exe");         p.WaitForInputIdle();         IntPtr h = p.MainWindowHandle;         SetForegroundWindow(h);         SendKeys.SendWait("k");         IntPtr processFoundWindow = p.MainWindowHandle;     } } 

Can someone help me to understand why it gives me an error on the DllImport line and on the public static line?

Does anyone have an idea, what can I do? Thank you.

Answer 1

You can't declare an extern local method inside of a method, or any other method with an attribute. Move your DLL import into the class:

using System.Runtime.InteropServices;   public class WindowHandling {     [DllImport("User32.dll")]     public static extern int SetForegroundWindow(IntPtr point);      public void ActivateTargetApplication(string processName, List<string> barcodesList)     {         Process p = Process.Start("notepad++.exe");         p.WaitForInputIdle();         IntPtr h = p.MainWindowHandle;         SetForegroundWindow(h);         SendKeys.SendWait("k");         IntPtr processFoundWindow = p.MainWindowHandle;     } }