foreach(DataRow row in dtMenu.Rows)
 {     
object value = row["ColumnName"];   
  if (value == DBNull.Value)        
 {
  Console.Writeln("Null");
} 
else       
{
Console.Writeln("Not Null");
}
} //end of foreach

if(dtmenu.Rows.count>0)
{
 //Ur code here
}

if(dtmenu.Tables[0].Rows.count>0)
{
 //Ur code here
}

SqlDataReader sdr= new SqlDataReader();
While(sdr.Read()
{
    /your code…
}
While(

while(DataTabe.Rows.Count)
{
// your code…
}

DataSet ds = new DataSet();
While(ds.Tables[0].Rows.Count)
{
// your code…
}

if(dtmenu.rows.count>0)
{
//TO-DO Here
}

if (dtmenu!= null)
 {
   if(dtmenu.Rows.Count>0) 
   {
      //DoSomething
   } 
}