how to fill data in comboBox. but error was found?

vinod jangir

try

{

string connString = @"Data Source=VINODKUMAR;Initial Catalog=ShreeSankalp;Persist Security Info=True;User ID=sa;Password=1234567890";

using (SqlConnection sqlConn = new SqlConnection(connString))

{

string sqlQuery = @"SELECT Batch No * from New Batchs";

SqlCommand cmd = new SqlCommand(sqlQuery, sqlConn);

SqlDataAdapter da = new SqlDataAdapter(cmd);

DataTable dt = new DataTable();

da.Fill(dt);

//dt.Columns.Add("Batch No", typeof (string));

comboBox1.DisplayMember = "Batch No";

comboBox1.DataSource = dt;

}

catch (Exception ex)

{

MessageBox.Show(ex.ToString());

MessageBox.Show("Please Enter Admission ID");

}

15 Replies

Know the answer? Post it — somebody with the same question will find it here.

Raja T11y ago
Accepted answer
try
{
con.Open();
da = new SqlDataAdapter("select BatchNo from Batches" , con);
dt = new DataTable();
da.Fill(dt);
//DataRow dr;
//dr = dt.NewRow();
//dr.ItemArray = new object[] { 0, "---Select an item---" };
//dt.Rows.InsertAt(dr, 0);
comboBox1.DisplayMember = "BatchNo";
comboBox1.ValueMember = "S.No";
comboBox1.DataSource = dt;
con.Close();
}
catch (Exception ex)
{
MessageBox.Show(ex.Message);
}

Which code are tried above code?
vinod jangir11y ago
yes i try but same problem
Raja T11y ago
Are you tried my solution?
vinod jangir11y ago
try
{
con.Open();
da = new SqlDataAdapter("select BatchNo from Batches" , con);
dt = new DataTable();
da.Fill(dt);
//DataRow dr;
//dr = dt.NewRow();
//dr.ItemArray = new object[] { 0, "---Select an item---" };
//dt.Rows.InsertAt(dr, 0);
comboBox1.DisplayMember = "BatchNo";
comboBox1.ValueMember = "S.No";
comboBox1.DataSource = dt;
con.Close();
}
catch (Exception ex)
{
MessageBox.Show(ex.Message);
}

I Got this problem
Object reference not set to an instance of an object.
Raja T11y ago
Hi Vinod, try like

string sqlQuery = @"SELECT BatchNo from Batches";
SqlCommand cmd = new SqlCommand(sqlQuery, sqlConn);
SqlDataAdapter da = new SqlDataAdapter(cmd);
DataSet ds = new DataSet();
da.Fill(ds);

comboBox1.ValueMember = "BatchNo";
comboBox1.DisplayMember = "BatchNo";

comboBox1.DataSource = ds.Tables[0];

Note : Please check in debug mode data set contains data or not
vinod jangir11y ago
comboBox2.DisplayMember = "BatchNo";
but same problem
Manas Mohapatra11y ago
string sqlQuery = @"SELECT BatchNo from Batches";
SqlCommand cmd = new SqlCommand(sqlQuery, sqlConn);
SqlDataAdapter da = new SqlDataAdapter(cmd);
DataTable dt = new DataTable();
da.Fill(dt);
comboBox2.DataSource = dt;
comboBox2.ValueMember = "BatchNo";
comboBox2.DisplayMember = "S.No";
See above two yellow marked code. You are fetching only BatchNo column in your query and you are using S.No as DisplayMember in combobox. Either you need fetch that column from DB or you need to use BatchNo as DisplayMember.

comboBox2.DisplayMember = "BatchNo";
vinod jangir11y ago
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Data.SqlClient;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
namespace ShriSankalp
{
public partial class Attendance : Form
{
public Attendance()
{
try
{
string connString = @"Data Source=VINODKUMAR;Initial Catalog=ShreeSankalp;Persist Security Info=True;User ID=sa;Password=1234567890";
using (SqlConnection sqlConn = new SqlConnection(connString))
{
string sqlQuery = @"SELECT BatchNo from Batches";
SqlCommand cmd = new SqlCommand(sqlQuery, sqlConn);
SqlDataAdapter da = new SqlDataAdapter(cmd);
DataTable dt = new DataTable();
da.Fill(dt);
comboBox1.DataSource = dt;
comboBox1.ValueMember = "BatchNo";
comboBox1.DisplayMember = "S.No";
}
}
catch (Exception ex)
{
MessageBox.Show(ex.ToString());
MessageBox.Show("Please Enter Admission ID");
}
InitializeComponent();
}

private void button1_Click(object sender, EventArgs e)
{
StuAtedLit reg = new StuAtedLit();
reg.Show();
}
private void button2_Click(object sender, EventArgs e)
{
this.Close();
}
}
}

it check
comboBox1.DataSource = dt;
and got error
"Object reference not set to an instance of an object."
Manas Mohapatra11y ago
Please provide in which line you are getting exact error and also provide whole code.
vinod jangir11y ago
same problem.
Abhishek Kumar11y ago
Please try to bind first ..
comboBox1.DataSource = dt;
comboBox1.ValueMember = "Batch No";
comboBox1.DisplayMember = "BatchID";
vinod jangir11y ago
Object reference not set to an instance of an object.
i got this error
Manas Mohapatra11y ago
Please comment below lines:

//DataRow dr;
//dr = dt.NewRow();
//dr.ItemArray = new object[] { 0, "---Select an item---" };
//dt.Rows.InsertAt(dr, 0);
vinod jangir11y ago
"input array is longer than the number of columns in this table"
error found
Manas Mohapatra11y ago
Try below code:

da.Fill(dt);
DataRow dr;
dr = dt.NewRow();
dr.ItemArray = new object[] { 0, "---Select an item---" };
dt.Rows.InsertAt(dr, 0);
comboBox1.DisplayMember = "Batch No";
comboBox1.ValueMember = "Batch No";
comboBox1.DataSource = dt;

Here I added DisplayMember, ValueMember as "Batch No". You can change per your requirement.