Compare new input data with record on table in ASP.Net

dt3 = getatable1();// table with 2 columns name,address
       dt4 = getatable2();// table with 2 columns name,address


       for (int i = 0; i < dt3.Rows.Count; i++)
       {
           for (int j = 0; j < dt3.Columns.Count-1; j++)
           {

               int k = 0;


               while (dt3.Rows[i][0].ToString()!= dt4.Rows[k][0].ToString() )
               {
                   k = k + 1;
               }

if (dt3.Rows[i][0].ToString()==dt4.Rows[k][0].ToString())//go on comparing like this
 //no need to go for this 2nd if and while loop, if ur 0th column of both tables is primary key or unique key

              
{
                   while (dt3.Rows[i][1].ToString() != dt4.Rows[k][1].ToString())
                    {

                        k++;

                    }
    Response.Write(dt3.Rows[i][0].ToString() + " =  " + dt4.Rows[k][1].ToString() + "<br>"); //use ur code for email/sms


                }