Error - Object reference not set to an instance of an object.

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Why this error is given Object reference not set to an instance of an object.

In the code line is given -
rs=ds.Tables["registration"].Select("umail='" + t1.Text.Trim() + "'");

My Code is given below.

C#

string u=t1.Text;
string m;
int r=0;
DataRow []rs;
rs=ds.Tables["registration"].Select("umail='" + t1.Text.Trim() + "'");
r=rs.Length;
if(t1.Text=="")
{System.Web.UI.WebControls.Label lbl1=new System.Web.UI.WebControls.Label();
lbl1.ForeColor=System.Drawing.Color.Blue;
lbl1.BackColor=System.Drawing.Color.Yellow;
lbl1.Text="Please Fill the form for entry";
ph1.Controls.Add(lbl1);
}else if(r>0)
{System.Web.UI.WebControls.Label lbl1=new System.Web.UI.WebControls.Label();
lbl1.ForeColor=System.Drawing.Color.Blue;
lbl1.BackColor=System.Drawing.Color.Yellow;
lbl1.Text="Record Already EXIST";
ph1.Controls.Add(lbl1);
}
else
{

com=con.CreateCommand();
com.CommandText="Insert into registration (uemail, ufname, ulname, udob, uloc, uphone, utown, ustate, uskill, urole,uindustry, utexp, urexp, ucv, upass) values('" + t1.Text.Trim() + "','" + t2.Text.Trim() + "','" + t3.Text.Trim() + "','" + dob.ToString() + "','" + ta1.Value + "','" + t4.Text.Trim() + "','" + d4.SelectedItem.Text + "','" + d5.SelectedItem.Text + "','" + t5.Text.Trim() + "','" + t6.Text.Trim() + "','" + d6.SelectedItem.Text + "','" + t7.Text.Trim() + "','" + t8.Text.Trim() + "','" + ta2.Value + "','" + p.ToString() + "')";
try
{com.ExecuteNonQuery();
System.Web.UI.WebControls.Label lbl1=new System.Web.UI.WebControls.Label();
lbl1.ForeColor=System.Drawing.Color.Blue;
lbl1.BackColor=System.Drawing.Color.Yellow;
lbl1.Text="Data Entred";
ph1.Controls.Add(lbl1);
}
catch(Exception ex)
{
Response.Write(ex.Message);
}
}
con.Close();

Posted 30-Oct-11 21:35pm

Janardan Pandey

Updated 30-Oct-11 21:41pm

RaisKazi

v2

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RaisKazi · Answer 1 · 2011-10-30T21:47:00

Solution 2

One possibility for this error I see is - value of ds or ds.Tables["registration"] could be null.

Debug your code and check value of ds.Tables["registration"].

Also you may add below condition in your code.

C#

if (ds.Tables.Count > 0 && ds.Tables["registration"] != null)
{
 rs = ds.Tables["registration"].Select("umail='" +    t1.Text.Trim() + "'");
 r = rs.Length;
}

Posted 30-Oct-11 21:47pm

RaisKazi

Updated 30-Oct-11 21:50pm

v2

Comments

Mehdi Gholam 31-Oct-11 3:47am

5'ed

RaisKazi 31-Oct-11 3:49am

Thank you Mehdi. :)

Mehdi Gholam · Answer 2 · 2011-10-30T21:46:00

Solution 1

Run your program under a debugger and see which part of line is a null object.

Posted 30-Oct-11 21:46pm

Mehdi Gholam

Shmuel Zang · Answer 3 · 2011-10-30T21:47:00

This exception is given when you try to access an object (a reference type) that is null (This object doesn't reference to any object's instance).

Probably, the value of ds is null or, there is no table that is called "registration".

You can change lines 3 - 6 to:

C#

DataTable dt = ds != null ? ds.Tables["registration"] : null;
DataRow[] rs = dt != null ? dt.Select("umail='" + t1.Text.Trim() + "'") : null;
int r = rs != null ? rs.Length : 0;