How to add interactive sorting for tablix and matrix header in the report?
Find the following steps for adding the interactive sorting for tablix or matrix report item header
Open the report in the report designer and right-click the text box in the column header that you want to add an interactive sort button, and then click Text Box Properties.
Click User sort as shown in the following image.
Provide the expressions in sort expression as shown in the following image.
You can repeat this action for multiple textboxes of the tablix or matrix headers.