private void button1_Click(object sender, EventArgs e)
        {
            string strRecordFilePath = "d:/dasda";
            string str=strRecordFilePath.Substring(0, 1).ToUpper();//取首字母并转为大写
            this.m_ChkDisk(str);
        }

　　  //strDisk应为大写，如 "D"

        private void m_ChkDisk(string strDisk)
        {
            if (strDisk == "")
                return;

            txtTotal.Text = GetHardDiskSpace(strDisk).ToString();
            txtFreeSpace.Text = GetHardDiskFreeSpace(strDisk).ToString();
            int a, b, c;
            a = Convert.ToInt32(txtTotal.Text);
            b = Convert.ToInt32(txtFreeSpace.Text);
            c = a - b;
           
            txtUse.Text=c.ToString();
        }

        ///  <summary>
        /// 获取指定驱动器的空间总大小(单位为B)
        ///  </summary>
        ///  <param name="str_HardDiskName">只需输入代表驱动器的字母即可 （大写）</param>
        ///  <returns> </returns>
        public static long GetHardDiskSpace(string str_HardDiskName)
        {
            long totalSize= new long();
            str_HardDiskName=str_HardDiskName +":\\";
            System.IO.DriveInfo[] drives = System.IO.DriveInfo.GetDrives();
            foreach (System.IO.DriveInfo drive in drives)
            {
                if (drive.Name == str_HardDiskName)
                {
                    totalSize = drive.TotalSize / (1024 * 1024 * 1024);
                }
            }
            return totalSize;
        }

        ///  <summary>
        /// 获取指定驱动器的剩余空间总大小(单位为B)
        ///  </summary>
        ///  <param name="str_HardDiskName">只需输入代表驱动器的字母即可 </param>
        ///  <returns> </returns>
        public static long GetHardDiskFreeSpace(string str_HardDiskName)
        {
            long freeSpace = new long();
            str_HardDiskName = str_HardDiskName + ":\\";
            System.IO.DriveInfo[] drives = System.IO.DriveInfo.GetDrives();
            foreach (System.IO.DriveInfo drive in drives)
            {
                if (drive.Name == str_HardDiskName)
                {
                    freeSpace = drive.TotalFreeSpace / (1024 * 1024 * 1024);
                }
            }
            return freeSpace;
        }