Asp.ent combined with two Datatable_ practical tips for the same structure

Wrote a function.

Copy Code code as follows:

<summary>
Merge two identical DataTable to return the merged results
</summary>
<param name= "DT1" ></param>
<param name= "DT2" ></param>
<returns></returns>
Public DataTable Combinethesamedatatable (DataTable Dt1, DataTable DT2)
{
if (DT1. Rows.Count = = 0 && dt2. Rows.Count = 0)
{
return new DataTable ();
}
if (DT1. Rows.Count = 0)
{
return DT2;
}
if (DT2. Rows.Count = 0)
{
return DT1;
}
DataSet ds = new DataSet ();
Ds. Tables.add (DT1. Copy ());
Ds. Merge (DT2. Copy ());
Return DS. Tables[0];
}

Because of the limited understanding of C #, so I do not understand why the dt1==null can not correctly judge the empty table, so the use of a number of lines of method. Also hope that high man can guide twos.