Logged-on Administrator deleting user

When logged on as Administrator, I need to remove a User JohnDoe

I have a gridview with ID "GVProfilesAndUsername" that returns a number records containing username's and UserID's. One of these records is that of JohnDoe, and I can select this record.

I am trying to write the VB code in a button click event that will use the membership functionality to delete JohnDoe and all his memberhip/profile info.  The code I have been trying is shown below, and I know the Membership.DeleteUser(user) statement is bad ( error type : membershipuser cannot be converted to string )

Can someone show me what the correct statement should be?  Here is the attempted code:

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Dim user As MembershipUser
user = Membership.GetUser(GVProfilesAndUserName.SelectedVa ...