Adding items to comboBox at runtime C# windows application

Question

I am reading values from database and assigning these values to combo but it didn't assign

try

{

objCls.objSqlCmd = new SqlCommand();

objCls.objSqlCmd.CommandType = CommandType.Text;

objCls.objSqlCmd.CommandText = "SELECT * FROM attributeValue WHERE attributeCode='" + attributeCode + "'";

objCls.objSqlCmd.Connection = clsObjects.objSqlCon;

clsObjects.objSqlDr = objCls.objSqlCmd.ExecuteReader();

while (clsObjects.objSqlDr.Read())

{

cmbDropDown.Items.Add(clsObjects.objSqlDr["v1"].ToString());

cmbDropDown.Items.Add(clsObjects.objSqlDr["v2"].ToString());

cmbDropDown.Items.Add(clsObjects.objSqlDr["v3"].ToString());

}

clsObjects.objSqlDr.Close();

}

catch (Exception ex)

{

clsFunction.CathExeption(ex);

}