如何使用COUNT函數有一個文本框在mysql中顯示在C＃中的Visual Studio搜索結果

Question

[在這裏輸入的形象描述] [1]

在我的代碼我使用一個DataGridView以顯示NIC號碼給客戶。然後，如果我們按計算按鈕，其他文本框必須填寫相關細節。一切都完成了。但伯爵仍然存在。我不能使用count命令，在mysql語法中顯示錯誤。

我想根據NIC號碼計數項目。非常感謝幫助。

private void dataGridView2_CellContentClick(object sender, DataGridViewCellEventArgs e) 
     { 
      if (e.RowIndex >= 0) 
      { 
       DataGridViewRow row = this.dataGridView2.Rows[e.RowIndex]; 
       textBox11.Text = row.Cells[1].Value.ToString(); 
      } 
     } 


private void button12_Click(object sender, EventArgs e) 
     { 

      if (textBox11.Text == null) 
      { 
       MessageBox.Show("Please select an Item"); 
      } 
      else 
      { 
       con.Open(); 
       string SelectQuery = "select * from cheque where national_id =" + (textBox11.Text); 
       MySqlCommand cmdDDDD = new MySqlCommand(SelectQuery, con); 
       mdr2 = cmdDDDD.ExecuteReader(); 

       if (mdr2.Read()) 
       { 
        textBox2.Text = mdr2.GetString("customer_name"); 

        con.Close(); 
        mdr2.Close(); 
        Countmmm(); 
       } 
       else 
       { 
        MessageBox.Show("No cheque from this ID"); 
        con.Close(); 
        mdr2.Close(); 
       } 
      } 
     } 

public void Countmmm() 
     { 

      con.Open(); 
      string MysqlStringnow = "SELECT count(national_id) from cheque ='" + textBox11.Text + "'"; 
      MySqlCommand mycqlcommandNow = new MySqlCommand(MysqlStringnow, con); 
      Int32 Rows_count = Convert.ToInt32(mycqlcommandNow.ExecuteScalar()); 
      mycqlcommandNow.Dispose(); 
      textBox4.Text = Rows_count.ToString(); 
      con.Close(); 

     } 


    [1]: https://i.stack.imgur.com/fS6D2.png 

Answer 1

你必須在SQL查詢sintax錯誤，你忘了 '其中national_id'，和it's不完整的，你應該這樣來做：

public void Countmmm() 

    { 

     con.Open(); 
     string MysqlStringnow = "SELECT count(national_id) from cheque where national_id='" + textBox11.Text + "'"; 
     MySqlCommand mycqlcommandNow = new MySqlCommand(MysqlStringnow, con); 
     Int32 Rows_count = Convert.ToInt32(mycqlcommandNow.ExecuteScalar()); 
     mycqlcommandNow.Dispose(); 
     textBox4.Text = Rows_count.ToString(); 
     con.Close(); 

    }