how to fill dropdownlist on page load

Question

4.00/5 (1 vote)

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Hello All,
I am getting this error for the following code to fill the dropdownlist 'ddlstuid' :

Error ocurredSystem.NullReferenceException: Object reference not set to an instance of an object. at IAP.Attendance.Page_Load(Object sender, EventArgs e).

pls tell me how to remove the above error.

code:

C#

SqlConnection myconn;
SqlCommand cmd;
string str = "Data Source=TIMSCDR\\SQLEXPRESS;Initial Catalog=IAP;Integrated Security=True";
SqlDataReader dr;

protected void Page_Load(object sender, EventArgs e)
{
    try
    {
        cmd = new SqlCommand("select stuid from attendance", myconn);
        myconn.Open();
        ddlstuid.Items.Clear();
        dr = cmd.ExecuteReader();
        if (dr != null)
        {
            while (dr.Read())
            {
                ddlstuid.Items.Add(dr["stuid"].ToString());
            }
        }
        myconn.Close();
    }
    catch (Exception e1)
    {
        Label45.Text = "Error ocurred" + e1;
    }

Thanks in Advance.

Posted 5-Jun-11 20:18pm

debo_india

Updated 5-Jun-11 20:37pm

Ramalinga Koushik

v2

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Comments

cuteband 6-Jun-11 2:21am

Is this a Web Based?

debo_india 6-Jun-11 2:34am

yep

6 solutions

Solution 7

try this:

VB

Dim strSQL As String
Dim connection As SqlConnection = New SqlConnection("Data Source=TIMSCDR\\SQLEXPRESS;Initial Catalog=IAP;Integrated Security=True")
strSQL = "Select [stuid] from [attendance]"
connection.Open()
Dim command As New SqlCommand(strSQL, connection)
dddiscipline.DataSource = command.ExecuteReader
ddlstuid.DataTextField = "stuid"
ddlstuid.DataValueField = "stuid"
ddlstuid.DataBind()
connection.Dispose()
connection.Close()

it works for me
pm me if it doesnt work

Posted 5-Jun-11 20:45pm

janwel

Comments

debo_india 6-Jun-11 3:12am

its giving error on the line : ddlstuid.DataSource = command.ExecuteReader;

janwel 6-Jun-11 4:14am

what does it say?

janwel 6-Jun-11 4:16am

plss put the exact error code

janwel 6-Jun-11 4:19am

what language are you using?

janwel 6-Jun-11 4:20am

LakshmiNarayana Nalluri has already have the answer plss use that code if your using C

Solution 6

C#

SqlConnection myconn;
      SqlCommand cmd;
      string str = "Data Source=TIMSCDR\\SQLEXPRESS;Initial Catalog=IAP;Integrated Security=True";
      SqlDataReader dr;

      protected void Page_Load(object sender, EventArgs e)
      {
         if(!Page.IsPostBack)
         {
          try
          {
              myconn = new SqlConnection(str); // --- Add this line
              cmd = new SqlCommand("select stuid from attendance", myconn);
              myconn.Open();
              ddlstuid.Items.Clear();
              dr = cmd.ExecuteReader();
              if (dr != null)
              {
                  while (dr.Read())
                  {
                      ddlstuid.Items.Add(dr["stuid"].ToString());
                  }
              }
              myconn.Close();
          }
          catch (Exception e1)
          {
              Label45.Text = "Error ocurred" + e1;
          }
         }

Posted 5-Jun-11 20:41pm

Abdul Quader Mamun

Solution 4

http://www.java2s.com/Tutorial/ASP.NET/0360__ADO.net-Database/ReaddatafromSQLserverandfillaspdropdownlistC.htm[^]

Refer this link

Posted 5-Jun-11 20:36pm

myes

Updated 5-Jun-11 20:38pm

v2

Comments

debo_india 6-Jun-11 3:01am

i tried this but its not working

Solution 2

public void bind()
{
sqldataadapter da=new sqldataadapter("select * from tname",cn);
datatable dt=new datatable();
da.fill(dt);
ddlstuid.datasource=dt;
ddlstuid.datatextfield="colnale";
ddlstuid.datavaluefield="colname";
ddlstuid.databind();
}

in page load
{
if(!ispostback)
{
bind();
}
}

Posted 5-Jun-11 20:24pm

LakshmiNarayana Nalluri

Comments

debo_india 6-Jun-11 2:34am

in the line: ddlstuid.datatextfield="colnale";

what is 'colnale'? did u mean 'colname'?

LakshmiNarayana Nalluri 6-Jun-11 2:46am

ya

janwel 6-Jun-11 4:46am

nicely done

Solution 1

You don't appear to assign anything to "myconn". Try adding

C#

cmd = new SqlCommand("select stuid from attendance", myconn);
myconn = new SqlConnection(str); // --- Add this line
myconn.Open();

Don't forget to dispose it in a finally block.

Posted 5-Jun-11 20:22pm

OriginalGriff

Comments

debo_india 6-Jun-11 2:28am

i tried this but its not working still

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Ra-one · Accepted Answer · 2011-06-05T20:38:00

Solution 5

Check 3 things......
1) you have a fields name stuid in your table or you misspelled it.
2) Add the solution suggested by OriginalGriff

myconn = new SqlConnection(str); // --- Add this line

3) Remove if(dr != null) rather add if(dr.hasRows)

Try out this.. If any problem Comment here..

Hope it helps

Posted 5-Jun-11 20:38pm

Ra-one

v2

Comments

debo_india 6-Jun-11 2:44am

i tried out your solution. it is giving an error on this line:
dr = cmd.ExecuteReader();

Ra-one 6-Jun-11 2:52am

It must not if you created SQLConnection before cmd.ExecuteReader()