using System; using System.Collections.Generic; using System.ComponentModel; using System.Data; using System.Drawing; using System.Linq; using System.Text; using System.Windows.Forms; using System.Runtime.InteropServices;//引用外部   namespace extern {     public partial class DllImportForm : Form     {         public DllImportForm()         {             InitializeComponent();         }           [DllImport("kernel32", SetLastError = true)]//声明和实现的连接         public static extern int GetCurrentDirectory(int a, StringBuilder b);//外部方法                 private void btnDisplay_Click(object sender, EventArgs e)         {             StringBuilder pathstring=new StringBuilder ();//返回路径             GetCurrentDirectory(300, pathstring);            this.listBox1.Items.Add (pathstring );           }     } }