Private void Button1_Click(object sender, System.EventArgs e) { con=new OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0;Data Source=D:signin.mdb;Persist Security Info=False"); string s; s="select * from login where username='" + TextBox1.Text + "'and password='" + TextBox2.Text + "'"; ad.SelectCommand.CommandText=s; ds=new DataSet(); ad.Fill(ds); if(ds.Tables[0].Rows.Count>0) { Label3.Text ="valid user"; } else Label3.Text="Invalid user"; }Whenever i am using adapter wizard there is no error. but through coding getting error as Object reference not set to an instance of an object. How to rectify it?

Interview Candidate
Sep 28th, 2006
5
8359

Showing Answers 1 - 5 of 5 Answers

Chakravarthi

Oct 5th, 2006

May be your no intializing the adapter class object . check once again the declaration & intiatlization block
ad = new OledbAdapter
ad.connection=con

Guru

Nov 5th, 2006

try
{
OledbConnection con=new OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0;Data Source=D:signin.mdb;Persist Security Info=False");
string s;
s="select * from login where username='" + TextBox1.Text + "'and password='" + TextBox2.Text + "'";
OledbDataaAdapter ad=new OledbDataAdaptead();
ad.SelectCommand.CommandText=s;
DataSet ds=new DataSet();
ad.Fill(ds);
if(ds.Tables[0].Rows.Count>0)
{
Label3.Text ="valid user";
}
else
Label3.Text="Invalid user";
}
catch(Exception ex)
{
Response.Write(ex.Message());
}