TRY THIS
dt3 = getatable1();
dt4 = getatable2();
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())
{
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>");
}