Combobox item when select displaying wrong record in textbox

Question

Hello all genius: My problem is I got two tables tbl_session where I have 'SessionID' 'SessionName' and tbl_Class where I have 'ClassID' 'SessionID' 'ClassName'  (SessionID [FK] of tbl_Class is link with Session_ID[PK] of tbl_Session ]. There are same 'ClassName' in tbl_Class whose SessionID and ClassID is different, Now my query is, if select ClassName from combobox then display ClassID in textbox. But the problem is I have same ClassName, So as per my query when I choose ClassName it shows the different ClassID, but I want to achieve the ClassID of the same ClassName that displays in my combobox.

 

Here is my code to fill combo_Class:

 

private void FillClass(int SessionID)

{

string str = "SELECT ClassId, ClassName FROM ClassMaster WHERE SessionID =@SessionID";

OleDbCommand cmd = new OleDbCommand(str, connection);

cmd.Parameters.AddWithValue("@SessionID", SessionID);

DataSet objDs = new DataSet();

OleDbDataAdapter dAdapter = new OleDbDataAdapter();

dAdapter.SelectCommand = cmd;

connection.Open();

dAdapter.Fill(objDs);

connection.Close();

if (objDs.Tables[0].Rows.Count > 0)

{

combo_Class.ValueMember = "ClassId";

combo_Class.DisplayMember = "ClassName";

combo_Class.DataSource = objDs.Tables[0];

}

}

 

 

//And here is the code to select class from combo_Class  and display  ClassID in textbox: 

 

 

private void combo_Class_SelectedIndexChanged(object sender, EventArgs e)

{

try

{

connection.Open();

OleDbCommand command = new OleDbCommand();

command.Connection = connection;

string query = " select * from ClassMaster where ClassName= '" + combo_Class.Text + "' ";

command.CommandText = query;

OleDbDataReader reader = command.ExecuteReader();

while (reader.Read())

{

txt_ClassId.Text = reader["ClassId"].ToString();

}

connection.Close();

}

catch (Exception ex)

{

MessageBox.Show("Error " + ex);

}

}

 

 // Please help me please...