---
title: Configure Identity primary key data type
author: AdrienTorris
description: This article outlines the steps for configuring the desired data type used for the ASP.NET Core Identity primary key.
keywords: ASP.NET Core,Identity,primary key
ms.author: scaddie
manager: wpickett
ms.date: 09/28/2017
ms.topic: article
ms.technology: aspnet
ms.prod: asp.net-core
uid: security/authentication/identity-primary-key-configuration
---
# Configure the ASP.NET Core Identity primary key data type

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.

## Customize the primary key data type

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`.

    [!code-csharp[Main](identity/sample/src/ASPNET-IdentityDemo-PrimaryKeysConfig/Models/ApplicationUser.cs?highlight=4&range=7-13)]

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`.
    
    [!code-csharp[Main](identity/sample/src/ASPNET-IdentityDemo-PrimaryKeysConfig/Models/ApplicationRole.cs?highlight=3&range=7-12)]
	
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.

    [!code-csharp[Main](identity/sample/src/ASPNET-IdentityDemo-PrimaryKeysConfig/Data/ApplicationDbContext.cs?highlight=3&range=9-26)]
	
1. Register the custom database context class when adding the Identity service in the app's startup class.

    # [ASP.NET Core 2.x](#tab/aspnetcore2x)
    
    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.
    
    [!code-csharp[Main](identity/sample/src/ASPNETv2-IdentityDemo-PrimaryKeysConfig/Startup.cs?highlight=6-8&range=25-37)]
    
    # [ASP.NET Core 1.x](#tab/aspnetcore1x)
    
    The `AddEntityFrameworkStores` method accepts a `TKey` argument indicating the primary key's data type.
    
    [!code-csharp[Main](identity/sample/src/ASPNET-IdentityDemo-PrimaryKeysConfig/Startup.cs?highlight=9-11&range=39-55)]
    
    ---

## Test the changes

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.

[!code-csharp[Main](identity/sample/src/ASPNET-IdentityDemo-PrimaryKeysConfig/Controllers/AccountController.cs?name=snippet_GetCurrentUserId&highlight=6)]