Display Country's name in Textbox

Question

Goal:
Display the name of countries in a list based on selection. For instance, if I select Australia and France, the country's name should display in the textbox. If I select (Select All), all the country's name shall be printed in the textbox.

Problem:
I do not know how to do it. I can retrieve one country but not many countries.

Answer 1

To display a comma-delimited string of selected parameters in a textbox, you would use an expression like:

=Join(Parameters!MyParameter.Label, ", ")

Since the parameter is multi-value its Label property will be an array, so Join takes the array and turns it back into a single string.