Hi Mouna,
Thanks for your interest in Syncfusion products.
We do not have support to set Minimum and Maximum size for the column width. But You can achieve your requirement by using the following code snippet on MultiColumnTreeView's ColumnResized event. For more information i have included the sample as follows.
[Code Snippet]
this.multiColumnTreeView1.Columns.VisibleColumns[0].Width = 120;
[Sample]
http://www.syncfusion.com/uploads/redirect.aspx?&team=support&file=TreeColumnAdv2842131582210.zipKindly have a look on the above sample and Please let us know if you need further assistance.
Regards,
Iniyen M.A.