C#ADO.NET:检查现有索引
我有以下代码,如果在表中找不到id,我想显示一条错误消息。任何正文都可以帮助吗C#ADO.NET:检查现有索引,c#,ado.net,C#,Ado.net,我有以下代码,如果在表中找不到id,我想显示一条错误消息。任何正文都可以帮助吗 private void button4_Click(object sender, EventArgs e) { conn = new MySqlConnection(cs); string sql = "select * from question where id=@id;"; MySqlCommand cmd = new MySqlCommand(sql, conn); conn
private void button4_Click(object sender, EventArgs e)
{
conn = new MySqlConnection(cs);
string sql = "select * from question where id=@id;";
MySqlCommand cmd = new MySqlCommand(sql, conn);
conn.Open();
cmd.Prepare();
cmd.Parameters.AddWithValue("@id", int.Parse(textBox1.Text));
MySqlDataReader rd = cmd.ExecuteReader();
string res = "";
while (rd.Read())
{
if (rd.HasRows==true)
{
res = string.Format("id={0} pid={1} question={2}", rd.GetInt32(0), rd.GetInt32(1), rd.GetString(2));
MessageBox.Show("found" + "\n" + res);
}
MessageBox.Show(" id not found");
}
在开始迭代读卡器之前,需要检查has行
if (rd.HasRows==true)
{
while (rd.Read())
{
// Do something here
}
}
else
{
// Show message here
}