检测空值并替换字符串C＃

Question

我目前在使用CSV到SQL转换器时遇到了一些问题。该程序用于创建命令以编辑数据库用户列表更新或添加新列表。我的问题是，如果用户没有在CSV文件中输入密码，我希望将其设置为用户ID。我当前有这个IF语句试图检测字符串是否为空但它总是说该字符串是空的，并给我设置弹出框，即使我在单元格中有文本。

if (password != null)
            {
                System.Windows.Forms.MessageBox.Show("Setting Password to User ID");
            }

我也尝试过password = password.replace（userid），但它不会改变字符串。如果有帮助，我已将我的整个代码包括在内。

        private void LoadBtn_Click(object sender, EventArgs e)
    {
        //Opens a browse box to allow the user to select which file, only CSV's allow allowed
        OpenFileDialog openFileDialog1 = new OpenFileDialog();
        openFileDialog1.Filter = "CSV Files (*.csv)|*.csv";
        openFileDialog1.FilterIndex = 1;

        //empties text box when clicked | loads file location and name to load directory text box at top
        if (openFileDialog1.ShowDialog() == System.Windows.Forms.DialogResult.OK)
        {
            ConvertedText.Text = string.Empty;
            LoadDirectory.Text = openFileDialog1.FileName.ToString();
        }
        string filename = LoadDirectory.Text;
        string[] Lines = File.ReadAllLines(filename);
        string[] Fields;


        for (int i = 1; i < Lines.Length; i++)
        {
            string outfile = "";
            Fields = Lines[i].Split(new char[] { ',' });
            string userid = Fields[0];
            string password = Fields[1];
            string fullname = Fields[2];
            string address = Fields[3];
            string telephone = Fields[4];
            string email = Fields[5];
            string role = Fields[6];
            string department = Fields[7];

            if (password != null)
            {
                System.Windows.Forms.MessageBox.Show("Setting Password to User ID");
            }

            outfile += "IF exists (SELECT USERID FROM WUSERS WHERE USERID='" + userid + "')" + Environment.NewLine;
            outfile += "begin" + Environment.NewLine;
            outfile += Environment.NewLine;

            outfile += "-- Update it" + Environment.NewLine;
            outfile += "print 'updated'" + Environment.NewLine;
            outfile += "update WUSERS set FULLNAME= '" + fullname + "' where userid= '" + userid + "'" + Environment.NewLine;
            outfile += "update WUSERS set PW= '" + password + "' where userid= '" + userid + "'" + Environment.NewLine;
            outfile += "update WUSERS set addr= '" + address + "' where userid= '" + userid + "'" + Environment.NewLine;
            outfile += "update WUSERS set telno= '" + telephone + "' where userid= '" + userid + "'" + Environment.NewLine;
            outfile += "update WUSERS set email= '" + email + "' where userid= '" + userid + "'" + Environment.NewLine;
            outfile += "update WUSERS set ROLEID= '" + role + "' where userid= '" + userid + "'" + Environment.NewLine;
            outfile += "update WUSERS set dept= '" + department + "' where userid= '" + userid + "'" + Environment.NewLine;
            outfile += "end" + Environment.NewLine;

            outfile += "else" + Environment.NewLine;
            outfile += "begin" + Environment.NewLine;
            outfile += "-- add it" + Environment.NewLine;
            outfile += "print 'added'" + Environment.NewLine;
            outfile += "insert into WUSERS (USERID,PW,FULLNAME,ADDR,TELNO,EMAIL,ROLEID,DEPT) Values ('" + userid + "','" + password + "','" + fullname + "','" + address + "','" + telephone + "','" + email + "','" + role + "','" + department + "')";
            outfile += Environment.NewLine;
            outfile += "end";
            outfile += Environment.NewLine;
            outfile += Environment.NewLine;
            outfile += Environment.NewLine;
            outfile += "-----------------------------------------------------------------------------------------------------------------------------------------------";
            outfile += Environment.NewLine;
            outfile += Environment.NewLine;
            outfile += Environment.NewLine;

            ConvertedText.AppendText(outfile);

        }

    }

提前感谢您的任何意见。

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