How can I include 'All' in a Variable Picklist

[AyokunleAdebisi]

I am building a tool using model builder in ArcGIS pro. I will like the user to be to select all in my variable pick-list;for instance i want the user to select all location (polygon).

[AyokunleAdebisi]

Hello Andrew, your tips have helped a lot but this is the problem now, whenever the location is empty it works but whenever i input "All locations" it gives warning  - -'The process did not execute because the precondition is false', Is there anything wrong with my model or logic. Please help me to check it up.

[Anonymous User]

This warning does not necessarily mean anything is wrong with the model -- it just means certain tools did not run, which is expected in some cases (for example, if you have a selection query for when the user chooses "All locations", and another query for when they choose another value, only one query should run, not both). 

[AyokunleAdebisi]

Thanks. it is working but the only warning I get now is " All input are current". which does not allow execution of final results..What could be the reason for " All input are current".

[AyokunleAdebisi]

.Thanks. it is working but the only warning I get now is " All input are not current". which does not allow execution of final results..What could be the reason for " All input are not current"