Convert from Entity Collection to List and Vice Versa

Question

Hello Everyone,

 

[1]. After getting data into EntityCollection I want to perform Custom Sorting operation. I feel custom sorting is not possible with EntityCollection (If possible, please suggest me).

 

Now the alternative I found is converting from EntityCollection to List and perform Sorting operation, then store it back to EntityCollection.

 

but I dont know how to perform this operation. Please help me.

 

[2]. If it is possible to do Custom sorting with Entity Collection, please help me for the below query.

 

If EntityCollection I have is => {1,2,3,4,5,6,7,8,9} 

 

when I click on column header,  

Result expected is => {1,2,3,9,8,7,6,5,4}  

if I click on column header again, it should sort back to => {1,2,3,4,5,6,7,8,9}

 

Thank you.