如何解决错误ApplicationRole“不包含采用参数1. [DbInitialize]的构造函数？

Question

我创建了 class ApplicationRole 并继承自 IdentityRole

using Microsoft.AspNetCore.Identity;

namespace ProjDAL.Entities
{
    public class ApplicationRole : IdentityRole
    {

    }
}

当我尝试添加新角色时出现错误：

if (await _roleManager.FindByNameAsync("Quality Manager") == null)
{
    await _roleManager.CreateAsync(new ApplicationRole("Quality Manager"));
}

'ApplicationRole "不包含接受参数1的构造函数。[DbInitialize]

更新：

我已经实现了构造函数：

public class ApplicationRole : IdentityRole
    {
        public ApplicationRole(string roleName) : base(roleName)
        {
        }
    }

但现在出现错误：

System.InvalidOperationException: No suitable constructor found for entity 
type 'ApplicationRole'. The following constructors had parameters that could 
not be bound to properties of the entity type: cannot bind 'roleName' 
in ApplicationRole(string roleName).

Answer 1

简答： 如下更改代码

public class ApplicationRole : IdentityRole<string>
{
    public ApplicationRole() : base()
    {
    }

    public ApplicationRole(string roleName) : base(roleName)
    {
    }
}

长版：

'ApplicationRole "does not contain a constructor that takes arguments 1. [DbInitialize]`

出现第一个错误是因为您试图通过

创建新角色

new ApplicationRole("Quality Manager")

但是，没有接受单个字符串作为参数的构造函数：

    public class ApplicationRole : IdentityRole
    {

    }

所以它抱怨

does not contain a constructor that takes arguments 1. [DbInitialize]

注意当没有显式构造函数时，C# 将为您create one by default。

但是，如果您添加如下构造函数：

public class ApplicationRole : IdentityRole
{
    public ApplicationRole(string roleName) : base(roleName)
    {
    }
}

只有一个构造函数接受 string 作为 roleName。请注意，这意味着 没有不带参数的构造函数 。由于此构造函数（不带参数）由 Identity 在内部使用，因此它抱怨 No suitable constructor found for entity type 'ApplicationRole'.

因此，如果您想通过以下方式创建 ApplicationRole：

new ApplicationRole("Quality Manager")

您需要同时创建 ApplicationRole() 和 ApplicationRole(string roleName) 构造函数。

如何解决错误ApplicationRole“不包含采用参数1. [DbInitialize]的构造函数？

How solve error ApplicationRole "does not contain a constructor that takes arguments 1. [DbInitialize]?

c#

asp.net-identity

asp.net-core