ASP.NET Core Identity allows you to configure the data type used to represent a primary key. Identity uses the `string` data type by default. You can override this behavior.
1. Create a custom implementation of the [IdentityUser](https://docs.microsoft.com/aspnet/core/api/microsoft.aspnetcore.identity.entityframeworkcore.identityuser-1) class. It represents the type to be used for creating user objects. In the following example, the default `string` type is replaced with `Guid`.
1. Create a custom implementation of the [IdentityRole](https://docs.microsoft.com/aspnet/core/api/microsoft.aspnetcore.identity.entityframeworkcore.identityrole-1) class. It represents the type to be used for creating role objects. In the following example, the default `string` type is replaced with `Guid`.
1. Create a custom database context class. It inherits from the Entity Framework database context class used for Identity. The `TUser` and `TRole` arguments reference the custom user and role classes created in the previous step, respectively. The `Guid` data type is defined for the primary key.
The `AddEntityFrameworkStores` method doesn't accept a `TKey` argument as it did in ASP.NET Core 1.x. The primary key's data type is inferred by analyzing the `DbContext` object.
Upon completion of the configuration changes, the property representing the primary key reflects the new data type. The following example demonstrates accessing the property in an MVC controller.
