Question

当查询时间过长时，经常会遇到这种情况。我已经定义了参数@no_registrasi，但是它仍然出错。

MySql.Data.MySqlClient.MySqlException：命令执行期间遇到致命错误。 ---> MySql.Data.MySqlClient.MySqlException：必须定义参数'@no_registrasi'。

这是我的代码：

        void Tombol_cari_simpanan1Click(object sender, EventArgs e)
    {
        string connectionString = "Server=localhost;User ID=root;Password=;Database=koperasi;Convert Zero Datetime=True;";
        MySql.Data.MySqlClient.MySqlConnection connect = new MySql.Data.MySqlClient.MySqlConnection(connectionString);
        connect.Open();
        string query = "select * from simpanan left join anggota on simpanan.no_registrasi = anggota.no_registrasi left join jenis_simpanan on simpanan.id_jenis_simpanan = jenis_simpanan.id_jenis_simpanan where simpanan.no_registrasi = @no_registrasi";
        MySql.Data.MySqlClient.MySqlCommand myCommand = new MySql.Data.MySqlClient.MySqlCommand(query, connect);
        myCommand.Parameters.AddWithValue("@no_registrasi", int.Parse(textbox_pencarian_no_registrasi.Text));
        MySql.Data.MySqlClient.MySqlDataReader reader=myCommand.ExecuteReader();
        connect.Close();
        mySqlDataAdapter = new MySql.Data.MySqlClient.MySqlDataAdapter(query, connect);
        DataSet DS = new DataSet();
        mySqlDataAdapter.Fill(DS);
        datagrid_simpanan.DataSource = DS.Tables[0];
        connect.Close();    
    }

Answer 1

因为您将参数添加到MySqlCommand myCommand对象中。

但是您也可以通过mySqlDataAdapter查询，该对象没有设置任何参数。

您不需要使用部分{p> MySqlCommand myCommand中的

，因为您没有使用

MySql.Data.MySqlClient.MySqlDataReader reader=myCommand.ExecuteReader();

我想你可以试试看。

void Tombol_cari_simpanan1Click(object sender, EventArgs e)
{
    string connectionString = "Server=localhost;User ID=root;Password=;Database=koperasi;Convert Zero Datetime=True;";
    string query = "select * from simpanan left join anggota on simpanan.no_registrasi = anggota.no_registrasi left join jenis_simpanan on simpanan.id_jenis_simpanan = jenis_simpanan.id_jenis_simpanan where simpanan.no_registrasi = @no_registrasi";

    MySql.Data.MySqlClient.MySqlConnection connect = new MySql.Data.MySqlClient.MySqlConnection(connectionString);
    connect.Open();

    mySqlDataAdapter = new MySql.Data.MySqlClient.MySqlDataAdapter(query, connect);
    DataSet DS = new DataSet();
    mySqlDataAdapter.SelectCommand.Parameters.AddWithValue("@no_registrasi", int.Parse(textbox_pencarian_no_registrasi.Text));
    mySqlDataAdapter.Fill(DS);
    datagrid_simpanan.DataSource = DS.Tables[0];
    connect.Close();
}

注意：

我会使用using关键字来包含

MySqlConnection connect = new MySqlConnection(connectionString)

由于connect对象离开范围时，它将自动调用IDisposable.Dispose()接口方法。

string connectionString = "Server=localhost;User ID=root;Password=;Database=koperasi;Convert Zero Datetime=True;";
string query = "select * from simpanan left join anggota on simpanan.no_registrasi = anggota.no_registrasi left join jenis_simpanan on simpanan.id_jenis_simpanan = jenis_simpanan.id_jenis_simpanan where simpanan.no_registrasi = @no_registrasi";
DataSet DS = new DataSet();
using (MySqlConnection connect = new MySqlConnection(connectionString))
{
    connect.Open();
    mySqlDataAdapter = new MySqlDataAdapter(query, connect);
    mySqlDataAdapter.SelectCommand.Parameters.AddWithValue("@no_registrasi", int.Parse(textbox_pencarian_no_registrasi.Text));
    mySqlDataAdapter.Fill(DS);
    datagrid_simpanan.DataSource = DS.Tables[0];
}

必须定义参数@

1 个答案: