只需删除拖放到.dbml文件中的表，然后重新拖动它们。清洁方案>重建方案>重建方案。

这对我很管用。

我没有做我自己的表格，我是用VS和SSMS，我遵循这个链接为ASP。净身份:https://learn.microsoft.com/en-us/aspnet/identity/overview/getting-started/adding-aspnet-identity-to-an-empty-or-existing-web-forms-project

即使一切正确，如果Identity列的数据类型不是int或long，也会出现此错误。我有单位列为十进制，虽然我只保存int值(我的坏)。更改数据库和底层模型中的数据类型为我解决了这个问题。

This occurs when you have a (Primary key) column that is not set to Is Identity to true in SQL and you don't pass explicit value thereof during insert. It will take the first row, then you wont be able to insert the second row, the error will pop up. This can be corrected by adding this line of code [DatabaseGenerated(DatabaseGeneratedOption.Identity)] in your PrimaryKey column and make sure its set to a data type int. If the column is the primary key and is set to IsIDentity to true in SQL there is no need for this line of code [DatabaseGenerated(DatabaseGeneratedOption.Identity)] this also occurs when u have a column that is not the primary key, in SQL that is set to Is Identity to true, and in your EF you did not add this line of code [DatabaseGenerated(DatabaseGeneratedOption.Identity)]

在该表的实体中，将DatabaseGenerated属性添加到标识插入设置的列之上:

例子:

[DatabaseGenerated(DatabaseGeneratedOption.Identity)]
public int TaskId { get; set; }

EF Core 3.x

引用Leniel Maccaferri，我有一个带有自动递增属性的表，称为ID(原始主键)和另一个属性称为Other_ID(新的主键)。最初ID是主键，但后来Other_ID需要成为新的主键。由于ID正在应用程序的其他部分使用，我不能只是从表中删除它。Leniel Maccaferri解决方案只适用于我之后，我添加了以下片段:

        entity.HasKey(x => x.Other_ID);
        entity.Property(x => x.ID).ValueGeneratedOnAdd();

完整代码片段如下(ApplicationDbContext.cs):

  protected override void OnModelCreating(ModelBuilder builder)
  {
        builder.ApplyConfigurationsFromAssembly(Assembly.GetExecutingAssembly());
        base.OnModelCreating(builder);
        builder.Entity<tablename>(entity =>
        {
            entity.HasKey(x => x.Other_ID);
            entity.Property(x => x.ID).ValueGeneratedOnAdd();
            entity.HasAlternateKey(x => new { x.Other_ID, x.ID });                
        });
        
    }

使用实体框架与这样的模型有同样的问题(我简化了原始代码):

public class Pipeline
{
  public Pipeline()
  {
     Runs = new HashSet<Run>();
  }

  public int Id {get; set;}
  public ICollection<Run> Runs {get;set;}
}

public class Run
{
  public int Id {get; set;}
  public int RequestId {get; set;}
  public Pipeline Pipeline {get;set;}
}

运行与管道有多对1的关系(一个管道可以运行多次)

在我的RunService中，我注入了dbcontext作为上下文。DbContext有一个Runs DbSet。我在RunService中实现了这个方法:

public async Task<Run> CreateAndInit(int requestId, int pplId)
{
  Pipeline pipeline = await pipelineService.Get(pplId).FirstOrDefaultAsync().ConfigureAwait(false);
  Run newRun = new Run {RequestId = requestId, Pipeline = pipeline};
  context.Runs.Add(newRun);
  await context.SaveChangesAsync().ConfigureAwait(false); // got exception in this line
  return newRun;
}

当方法执行时，我得到了这个异常:

Exception has occurred: CLR/Microsoft.EntityFrameworkCore.DbUpdateException
Exception thrown: 'Microsoft.EntityFrameworkCore.DbUpdateException' in System.Private.CoreLib.dll: 'An error occurred while updating the entries. See the inner exception for details.'
 Inner exceptions found, see $exception in variables window for more details.
 Innermost exception     Microsoft.Data.SqlClient.SqlException : Cannot insert explicit value for identity column in table 'Pipelines' when IDENTITY_INSERT is set to OFF.

对我来说，解决方案是将对象和关系的创建分开

public async Task<Run> CreateAndInit(int requestId, int pplId)
{
  Pipeline pipeline = await pipelineService.Get(pplId).FirstOrDefaultAsync().ConfigureAwait(false);
  Run newRun = new Run {RequestId = requestId};
  context.Runs.Add(newRun);
  newRun.Pipeline = pipeline; // set the relation separately
  await context.SaveChangesAsync().ConfigureAwait(false); // no exception
  return newRun;
}