IIF usage of datatable

Let's look at the example.

Code

 1 datatable dt = dgvshowall. datasource as datatable;
2 DT. Columns. Add (New datacolumn ("doctype", typeof (string )));
3 DT. columns ["doctype"]. expression = "IIF (check_type = 1, 'purchase warehouse receiving ', IIF (check_type = 2, 'check warehouse receiving', IIF (check_type = 3, 'migrate warehouse receiving warehouse ', IIF (check_type = 4, 'sale return', 'other warehouse receiving '))))";

 

The case when version .. Or am I the only solution?