如果存在具有角色的用户 ID，如何阻止 ASP.NET 标识删除该角色？

Question

这是表的 SQL：

CREATE TABLE [dbo].[AspNetUserRoles] (
    [UserId] INT NOT NULL,
    [RoleId] INT NOT NULL,
    CONSTRAINT [PK_dbo.AspNetUserRoles] PRIMARY KEY CLUSTERED ([UserId] ASC, [RoleId] ASC),
    CONSTRAINT [FK_dbo.AspNetUserRoles_dbo.AspNetRoles_RoleId] FOREIGN KEY ([RoleId]) REFERENCES [dbo].[AspNetRoles] ([Id]) ON DELETE CASCADE,
    CONSTRAINT [FK_dbo.AspNetUserRoles_dbo.AspNetUsers_UserId] FOREIGN KEY ([UserId]) REFERENCES [dbo].[AspNetUsers] ([Id]) ON DELETE CASCADE
);
CREATE TABLE [dbo].[AspNetRoles] (
    [Id]   INT            IDENTITY (1, 1) NOT NULL,
    [Name] NVARCHAR (256) NOT NULL,
    CONSTRAINT [PK_dbo.AspNetRoles] PRIMARY KEY CLUSTERED ([Id] ASC)
);

CREATE TABLE [dbo].[AspNetUsers] (
    [Id]                   INT            IDENTITY (1, 1) NOT NULL,
    [FirstName]            NVARCHAR (MAX) NULL,
    [LastName]             NVARCHAR (MAX) NULL,
    CONSTRAINT [PK_dbo.AspNetUsers] PRIMARY KEY CLUSTERED ([Id] ASC)
);

GO
CREATE UNIQUE NONCLUSTERED INDEX [UserNameIndex]
    ON [dbo].[AspNetUsers]([UserName] ASC);

有人可以帮我吗？我想要的是，当有一个用户被分配到一个角色时，我希望尝试删除该角色失败。

Answer 1

您的问题来自第 ON DELETE CASCADE 行。此行表示具有连接到要删除的记录的外键的所有记录本身都将被删除。

你可能想要ON DELETE NO ACTION.这将做你想要的。您应该能够找到查询调用的返回值是否删除了任何内容（- 它应该是包含更改的行数的整数）。