对于那些使用AutoMapper的人 如果您正在更新一个实体，该实体具有指向另一个实体(或多个实体)的外键，请确保所有的外实体都将其主键设置为数据库生成(或对MySQL自动递增)。

例如:

public class BuyerEntity
{
    [Key]
    public int BuyerId{ get; set; }

    public int Cash { get; set; }

    public List<VehicleEntity> Vehicles { get; set; }

    public List<PropertyEntity> Properties { get; set; }

}

Vehicles和Properties存储在不同于Buyers的表中。当你添加一个新的买家时，AutoMapper和EF会自动更新车辆和属性表，所以如果你没有在这些表上设置自动增量(就像我没有)，那么你会看到来自OP的问题的错误。

我也遇到了同样的问题。

我使用EF 6，代码优先+迁移。 问题是我们的DBA在抛出错误的表上创建了一个约束。

我在使用Telerik的RadGrid时遇到了这个问题。我将主键设置为只读的绑定列。如果列是display="false"，它会工作得很好，但readonly="true"导致了问题。我通过将绑定列display=false并添加一个单独的模板列来解决这个问题

<telerik:GridBoundColumn HeaderText="Shouldnt see" Display="false" 
     UniqueName="Id" DataField="Id">
</telerik:GridBoundColumn>
<telerik:GridTemplateColumn HeaderText="Id" UniqueName="IdDisplay">
    <ItemTemplate>
        <asp:Label ID="IDLabel" runat="server" 
            Text='<%# Eval("Id") %>'></asp:Label>                               
    </ItemTemplate>
</telerik:GridTemplateColumn> 

我在使用异步方法时偶尔会得到这个错误。自从我切换到同步方法后就没有发生过。

偶尔错误:

[Authorize(Roles = "Admin")]
[HttpDelete]
[Route("file/{id}/{customerId}/")]
public async Task<IHttpActionResult> Delete(int id, int customerId)
{
    var file = new Models.File() { Id = id, CustomerId = customerId };
    db.Files.Attach(file);
    db.Files.Remove(file);

    await db.SaveChangesAsync();

    return Ok();
}

一直有效:

[Authorize(Roles = "Admin")]
[HttpDelete]
[Route("file/{id}/{customerId}/")]
public IHttpActionResult Delete(int id, int customerId)
{
    var file = new Models.File() { Id = id, CustomerId = customerId };
    db.Files.Attach(file);
    db.Files.Remove(file);

    db.SaveChanges();

    return Ok();
}

我也有同样的问题，@webtrifusion的答案帮助我找到了解决方案。

我的模型使用实体ID上的绑定(排除)属性，这导致实体ID的值在HttpPost上为零。

namespace OrderUp.Models
{
[Bind(Exclude = "OrderID")]
public class Order
{
    [ScaffoldColumn(false)]
    public int OrderID { get; set; }

    [ScaffoldColumn(false)]
    public System.DateTime OrderDate { get; set; }

    [Required(ErrorMessage = "Name is required")]
    public string Username { get; set; }
    }
}   

Got the same problem when removing item from table(ParentTable) that was referenced by another 2 tables foreign keys with ON DELETE CASCADE rule(RefTable1, RefTable2). The problem appears because of "AFTER DELETE" trigger at one of referencing tables(RefTable1). This trigger was removing related record from ParentTable as result RefTable2 record was removed too. It appears that Entity Framework, while in-code was explicitly set to remove ParentTable record, was removing related record from RefTable1 and then record from RefTable2 after latter operation this exception was thrown because trigger already removed record from ParentTable which as results removed RefTable2 record.