C＃具有獲取

Question

private void TxtFarmerCode_TextChanged(object sender, EventArgs e) 
     { 
      try 
      { 
       cmd.Open(); 
       cmd = new SqlCommand("Select farmername, from cottonpurchase where farmercode=@aa", conn); 
       cmd.Parameters.Add("@aa", SqlDbType.Int).Value = TxtFarmerCode.Text; 
       dr = cmd.ExecuteReader(); 
       if (dr.HasRows == false) 
       { 
        throw new Exception(); 
       } 
       if (dr.Read()) 
       { 
        // textBox1.Text = dr[0].ToString(); Since U r going to give the ID and retrieve in textBox1. 
        TxtFarmerName.Text = dr[0].ToString(); 
        //textBox3.Text = dr[1].ToString(); 
        //textBox4.Text = dr[2].ToString(); 
        //textBox7.Text = dr[3].ToString(); 
        //dateTimePicker1.Text = dr[4].ToString(); 
        //dateTimePicker2.Text = dr[5].ToString(); 
        //textBox5.Text = dr[6].ToString(); 
       } 
      } 
      catch 
      { 
      // lblError = "THE GIVEN ID IS UNAVAILABLE"; 
      } 
      finally 
      { 
       conn.Close(); 
      } 

Answer 1

你缺少連接塊的一些錯誤（不管你要連接到更換connectionString）：

using (SqlConnection conn= new SqlConnection(
      connectionString)) 
    { 
     //You have cmd.Open it should be connection 
     conn.Open(); 
     cmd = new SqlCommand("Select farmername, from cottonpurchase where farmercode=@aa", conn); 
     cmd.Parameters.Add("@aa", SqlDbType.Int).Value = TxtFarmerCode.Text; 
     dr = cmd.ExecuteReader(); 
     if (dr.HasRows == false) 
     { 
      throw new Exception(); 
     } 
     if (dr.Read()) 
     { 
     // textBox1.Text = dr[0].ToString(); Since U r going to give the ID and retrieve in textBox1. 
     TxtFarmerName.Text = dr[0].ToString(); 
     //textBox3.Text = dr[1].ToString(); 
     //textBox4.Text = dr[2].ToString(); 
     //textBox7.Text = dr[3].ToString(); 
     //dateTimePicker1.Text = dr[4].ToString(); 
     //dateTimePicker2.Text = dr[5].ToString(); 
     //textBox5.Text = dr[6].ToString(); 
     } 
    } 
    catch 
    { 
     // lblError = "THE GIVEN ID IS UNAVAILABLE"; 
    } 
    finally 
    { 
     conn.Close(); 
    } 
    } 

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邊注... NEVER做catch {}