how we bind textbox on the basis of combobox selected index change event

Question

I Have a Combo box which is filled on page _load from Database now i want to bind the text boxes in the form based on selected value of combo box 
I Have Tried this one but  not working.. so plz help me 


private void cmbTab2RollNumber_SelectedIndexChanged(object sender, EventArgs e)
{
DataTable dt1=new DataTable ("StudentDetail");
int i=1;
for(i=1;i<cmbTab2RollNumber.SelectedIndex;i++)
{
txtTab2Name.Text = dt1.Rows[i].ToString();
}
}





Thanks