当我的查询太长时,我经常遇到这种情况。我定义了参数@no_registrasi,还是报错。
MySql.Data.MySqlClient.MySqlException: Fatal error encountered during command execution. ---> MySql.Data.MySqlClient.MySqlException: Parameter '@no_registrasi' must be defined.
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();
}
最佳答案
因为你在 MySqlCommand myCommand
对象中添加了参数。
但是你也通过mySqlDataAdapter
查询,那个对象没有设置任何参数。
从你关于 MySqlCommand myCommand
部分的代码是不必要的,因为你没有使用
MySql.Data.MySqlClient.MySqlDataReader reader=myCommand.ExecuteReader();
我想你可以试试这个。
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)
因为当 connect
对象离开作用域时,它会自动调用 IDisposable.Dispose()
接口(interface)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];
}
关于c# - 必须定义参数@,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/51280676/