如何在3层项目中创建备份时获得.bak扩展

Question

当单击备份btn时，它打开了一个savefiledialog框，但在保存为类型代码时找不到.bak扩展: private (对象发送方，EventArgs e)

     {             label4.Visible = false;

        DataSet ds = SqlGetData.GetData1("select srvname  from sysservers  where srvproduct='SQL Server'");

        for (int m = 0; m < ds.Tables[0].Rows.Count; m++)
        {
            cbserver.Items.Add(ds.Tables[0].Rows[0][m].ToString());
        }
    } 

私有comboBox1_SelectedIndexChanged(对象发送方，EventArgs e) { cbdb.Items.Clear()；DataSet ds =SqlGetData.GetData1(“从系统数据库中选择名称”)；for (int m= 0；m< ds.Tables.Rows.Count；m++) {cbdb.Items.Clear}

    private void button1_Click(object sender, EventArgs e)
    {

        blank("backup");


    }

    public void blank(string str)
    {
        if (string.IsNullOrEmpty(cbserver.Text) | string.IsNullOrEmpty(cbdb.Text))
        {

            label4.Visible = true;
            MessageBox.Show("Server Name & Database can not be Blank");
            return;

        }
        else
        {
            if (str == "backup")
            {
                saveFileDialog1.FileName = cbdb.Text;
                saveFileDialog1.ShowDialog();
                string s = null;
                s = saveFileDialog1.FileName;
                saveFileDialog1.Filter = "All Files|*.bak";
                query("Backup database " + cbdb.Text + " to disk='" + s + "'");

                label4.Visible = true;
                label4.Text = "Database BackUp has been created successful";



            }
        }

Answer 1

移动行，将筛选器设置为在显示对话框之前。

saveFileDialog1.Filter = "All Files|*.bak"
saveFileDialog1.ShowDialog();