To assign each User ID in dt_Users to a List variable Users_List, the Item property of the Add To Collection activity should be configured as:

CurrentRow(0).ToString

This expression accesses the value of the first column (index 0) in the current row of the dt_Users datatable using the CurrentRow variable. The CurrentRow variable is a DataRow object that represents the row that is being iterated in the For Each Row activity. The expression uses the ToString method to convert the value of the User ID column to a string type. The expression returns the User ID value as a string, which is then added to the Users_List variable by the Add To Collection activity1. For example, if the dt_Users datatable has the following values:

User ID

Name

101

John

102

Mary

103

Bob

Then the expression CurrentRow(0).ToString will return 101, 102, and 103 as the User ID values in each iteration of the For Each Row activity, and these values will be added to the Users_List variable.