ADO.NET :: Check For Duplicate Records

I want to check for duplicate records,if the record is already inserted then "record has already been inserted" should appear or else if its a new record then it should be inserted.. This function is inserting even if it exists and showing the error msg..

Sub CheckForDuplicateRec()
Dim da As SqlDataAdapter
Dim ds As New DataSet
Dim dt As New DataTable
cmd = New SqlCommand("Select * from Table3 where Name='" & txtname.Text & "' AND FName='" & txtfathersname.Text & "' AND MName='" & txtmothername.Text & "' AND Add1='" & txtadd.Text & "' AND Add2='" & txtadd2.Text & "' AND Add3='" & txtadd3.Text & "'
AND City='" & txtcity.Text & "' AND State='" & ddlstates.SelectedValue & "' AND Pincode=" & txtpincode.Text & "", con)
da = New SqlDataAdapter(cmd)
da.Fill(ds)
dt = ds.Tables("Table3")
If dt.Rows.Count = 0 Then
cmd = New SqlCommand("Insert into Table3 (Name,FName,MName,Add1,Add2,Add3,City,State,PinCode) values('" & txtname.Text & "','" & txtfathersname.Text & "','" & txtmothername.Text & "','" & txtadd.Text & "','" & txtadd2.Text & "','" & txtadd3.Text & "','"
& txtcity.Text & "','" & ddlstates.SelectedValue & "','" & txtpincode.Text & "')", con)
cmd.ExecuteNonQuery()
Else
lblError.Text = "Records already exists"
End If
End Sub