如何使用EF6和SQL Server捕获UniqueKey Violation异常？

Question

我的一个表有一个唯一的密钥,当我尝试插入一个重复的记录时,它会按预期抛出异常.但我需要区分唯一的密钥异常,以便我可以为唯一的密钥约束违规自定义错误消息.

我发现所有的解决方案在网上提出投ex.InnerException给System.Data.SqlClient.SqlException和检查,如果Number属性等于2601或2627,如下所示:

try
{
    _context.SaveChanges();
}
catch (Exception ex)
{
    var sqlException = ex.InnerException as System.Data.SqlClient.SqlException;

    if (sqlException.Number == 2601 || sqlException.Number == 2627)
    {
        ErrorMessage = "Cannot insert duplicate values.";
    }
    else
    {
        ErrorMessage = "Error while saving data.";
    }
}

但问题是,铸造ex.InnerException到System.Data.SqlClient.SqlException原因无效的转换错误,因为ex.InnerException实际上是一个类型的System.Data.Entity.Core.UpdateException,不是System.Data.SqlClient.SqlException.

上面的代码有什么问题？如何捕获Unique Key Constraint违规？

Answer 1

使用EF6和DbContextAPI(对于SQL Server),我目前正在使用这段代码:

try
{
  // Some DB access
}
catch (Exception ex)
{
  HandleException(ex);
}

public virtual void HandleException(Exception exception)
{
  if (exception is DbUpdateConcurrencyException concurrencyEx)
  {
    // A custom exception of yours for concurrency issues
    throw new ConcurrencyException();
  }
  else if (exception is DbUpdateException dbUpdateEx)
  {
    if (dbUpdateEx.InnerException != null
            && dbUpdateEx.InnerException.InnerException != null)
    {
      if (dbUpdateEx.InnerException.InnerException is SqlException sqlException)
      {
        switch (sqlException.Number)
        {
          case 2627:  // Unique constraint error
          case 547:   // Constraint check violation
          case 2601:  // Duplicated key row error
                      // Constraint violation exception
            // A custom exception of yours for concurrency issues
            throw new ConcurrencyException();
          default:
            // A custom exception of yours for other DB issues
            throw new DatabaseAccessException(
              dbUpdateEx.Message, dbUpdateEx.InnerException);
        }
      }

      throw new DatabaseAccessException(dbUpdateEx.Message, dbUpdateEx.InnerException);
    }
  }

  // If we're here then no exception has been thrown
  // So add another piece of code below for other exceptions not yet handled...
}

正如您所提到的UpdateException,我假设您正在使用ObjectContextAPI,但它应该是类似的.

Answer 2

就我而言,我正在使用EF 6并在我的模型中修饰其中一个属性:

[Index(IsUnique = true)]

为了捕获违规行为,我使用C#7执行以下操作,这变得更加容易:

protected async Task<IActionResult> PostItem(Item item)
{
  _DbContext.Items.Add(item);
  try
  {
    await _DbContext.SaveChangesAsync();
  }
  catch (DbUpdateException e)
  when (e.InnerException?.InnerException is SqlException sqlEx && 
    (sqlEx.Number == 2601 || sqlEx.Number == 2627))
  {
    return StatusCode(StatusCodes.Status409Conflict);
  }

  return Ok();
}

请注意,这只会捕获唯一的索引约束违规.

Answer 3

我认为显示一些代码可能很有用，不仅可以处理重复行异常，还可以提取一些可用于编程目的的有用信息。例如撰写自定义消息。

该Exception子类使用正则表达式来提取数据库表名称、索引名称和键值。

public class DuplicateKeyRowException : Exception
{
    public string TableName { get; }
    public string IndexName { get; }
    public string KeyValues { get; }

    public DuplicateKeyRowException(SqlException e) : base(e.Message, e)
    {
        if (e.Number != 2601) 
            throw new ArgumentException("SqlException is not a duplicate key row exception", e);

        var regex = @"\ACannot insert duplicate key row in object \'(?<TableName>.+?)\' with unique index \'(?<IndexName>.+?)\'\. The duplicate key value is \((?<KeyValues>.+?)\)";
        var match = new System.Text.RegularExpressions.Regex(regex, System.Text.RegularExpressions.RegexOptions.Compiled).Match(e.Message);

        Data["TableName"] = TableName = match?.Groups["TableName"].Value;
        Data["IndexName"] = IndexName = match?.Groups["IndexName"].Value;
        Data["KeyValues"] = KeyValues = match?.Groups["KeyValues"].Value;
    }
}

该类DuplicateKeyRowException很容易使用...只需创建一些错误处理代码，就像之前的答案一样...

public void SomeDbWork() {
    // ... code to create/edit/update/delete entities goes here ...
    try { Context.SaveChanges(); }
    catch (DbUpdateException e) { throw HandleDbUpdateException(e); }
}

public Exception HandleDbUpdateException(DbUpdateException e)
{
    // handle specific inner exceptions...
    if (e.InnerException is System.Data.SqlClient.SqlException ie)
        return HandleSqlException(ie);

    return e; // or, return the generic error
}

public Exception HandleSqlException(System.Data.SqlClient.SqlException e)
{
    // handle specific error codes...
    if (e.Number == 2601) return new DuplicateKeyRowException(e);

    return e; // or, return the generic error
}

Answer 4

// put this block in your loop
try
{
   // do your insert
}
catch(SqlException ex)
{
   // the exception alone won't tell you why it failed...
   if(ex.Number == 2627) // <-- but this will
   {
      //Violation of primary key. Handle Exception
   }
}

编辑:

您也可以只检查异常的消息组件.像这样的东西:

if (ex.Message.Contains("UniqueConstraint")) // do stuff

Answer 5

try
{
   // do your insert
}
catch(Exception ex)
{
   if (ex.GetBaseException().GetType() == typeof(SqlException))
   {
       Int32 ErrorCode = ((SqlException)ex.InnerException).Number;
       switch(ErrorCode)
       {
          case 2627:  // Unique constraint error
              break;
          case 547:   // Constraint check violation
              break;
          case 2601:  // Duplicated key row error
              break;
          default:
              break;
        }
    }
    else
    {
       // handle normal exception
    }
}