C＃在获取时有一些错误

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

您缺少连接块（将connectionString替换为您要连接的任何内容）：

  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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旁注…… 永远不要catch {}