尝试将非空字符串设置为“System.Int32”类型

实体框架抛出此异常：

“BranchIdentity”的“PasswordIterations”属性无法设置为“System.String”值。您必须将此属性设置为“System.Int32”类型的非空值。

它抛出在这条线上：

// Validate uniqueness or email and username
var user = sqlStorage.BranchIdentities.FirstOrDefault(i => i.Username.ToLower() == viewModel.Username.ToLower());

仅当存在与查询匹配的实体时才会引发异常。如果没有匹配项，则不会引发异常。

我的 BranchIdentity 模型：

namespace Branch.Models.Sql
{
    public class BranchIdentity
    {
        [Key]
        public int Id { get; set; }

        [Required]
        public string Username { get; set; }

        [Required]
        public string PasswordHash { get; set; }

        [Required]
        public string PasswordSalt { get; set; }

        [Required]
        public int PasswordIterations { get; set; }

        [Required]
        public string Email { get; set; }

        [Required]
        public string FullName { get; set; }

        public virtual ICollection<BranchIdentitySession> BranchIdentitySessions { get; set; } 

        public virtual BranchRole BranchRole { get; set; }

        public virtual GamerIdentity GamerIdentity { get; set; }
    }
}

我的架构（取自 sql 数据库）- 使用代码优先迁移自动生成：

CREATE TABLE [dbo].[BranchIdentities] (
    [Id]                 INT            IDENTITY (1, 1) NOT NULL,
    [Username]           NVARCHAR (MAX) NOT NULL,
    [PasswordHash]       NVARCHAR (MAX) NOT NULL,
    [PasswordSalt]       NVARCHAR (MAX) NOT NULL,
    [PasswordIterations] INT            NOT NULL,
    [Email]              NVARCHAR (MAX) NOT NULL,
    [BranchRole_Id]      INT            NULL,
    [GamerIdentity_Id]   INT            NULL,
    [FullName]           NVARCHAR (MAX) DEFAULT ('') NOT NULL,
    CONSTRAINT [PK_dbo.BranchIdentities] PRIMARY KEY CLUSTERED ([Id] ASC),
    CONSTRAINT [FK_dbo.BranchIdentities_dbo.BranchRoles_BranchRole_Id] FOREIGN KEY ([BranchRole_Id]) REFERENCES [dbo].[BranchRoles] ([Id]),
    CONSTRAINT [FK_dbo.BranchIdentities_dbo.GamerIdentities_GamerIdentity_Id] FOREIGN KEY ([GamerIdentity_Id]) REFERENCES [dbo].[GamerIdentities] ([Id])
);

我尝试过制作PasswordIterations可以为空，但无济于事。

听起来您的架构和实体不匹配，您首先发布了代码生成的代码，但自创建表以来可能已经发生了变化。查看 SQL Server 管理器中的表并仔细检查该列的数据类型。