对于Azure函数，我们使用这个简单的扩展Microsoft.Extensions.Logging.ILogger

public static class LoggerExtensions
{
    public static void Error(this ILogger logger, string message, Exception exception)
    {
        if (exception is DbEntityValidationException dbException)
        {
            message += "\nValidation Errors: ";
            foreach (var error in dbException.EntityValidationErrors.SelectMany(entity => entity.ValidationErrors))
            {
                message += $"\n * Field name: {error.PropertyName}, Error message: {error.ErrorMessage}";
            }
        }

        logger.LogError(default(EventId), exception, message);
    }
}

以及示例用法:

try
{
    do something with request and EF
}
catch (Exception e)
{
    log.Error($"Failed to create customer due to an exception: {e.Message}", e);
    return await StringResponseUtil.CreateResponse(HttpStatusCode.InternalServerError, e.Message);
}

在调试过程中通过检查错误来快速找到有意义的错误消息:

添加一个快速手表: ((System.Data.Entity.Validation.DbEntityValidationException)例外)美元.EntityValidationErrors 向下钻取EntityValidationErrors，如下所示: > ValidationErrors >(收集项，如[0])> ErrorMessage

Actually, this is just the validation issue, EF will validate the entity properties first before making any changes to the database. So, EF will check whether the property's value is out of range, like when you designed the table. Table_Column_UserName is varchar(20). But, in EF, you entered a value that longer than 20. Or, in other cases, if the column does not allow to be a Null. So, in the validation process, you have to set a value to the not null column, no matter whether you are going to make the change on it. I personally, like the Leniel Macaferi answer. It can show you the detail of the validation issues

正如Martin所指出的，在DbEntityValidationResult中有更多信息。我发现在每条消息中同时获取POCO类名和属性名很有用，并且希望避免为此在所有[Required]标记上编写自定义ErrorMessage属性。

以下对Martin代码的调整为我解决了这些细节问题:

// Retrieve the error messages as a list of strings.
List<string> errorMessages = new List<string>();
foreach (DbEntityValidationResult validationResult in ex.EntityValidationErrors)
{
    string entityName = validationResult.Entry.Entity.GetType().Name;
    foreach (DbValidationError error in validationResult.ValidationErrors)
    {
        errorMessages.Add(entityName + "." + error.PropertyName + ": " + error.ErrorMessage);
    }
}

要查看EntityValidationErrors集合，请将以下Watch表达式添加到Watch窗口。

((System.Data.Entity.Validation.DbEntityValidationException)$exception).EntityValidationErrors

我使用的是visual studio 2013

在代码中使用try块

try
{
    // Your code...
    // Could also be before try if you know the exception occurs in SaveChanges

    context.SaveChanges();
}
catch (DbEntityValidationException e)
{
    foreach (var eve in e.EntityValidationErrors)
    {
        Console.WriteLine("Entity of type \"{0}\" in state \"{1}\" has the following validation errors:",
            eve.Entry.Entity.GetType().Name, eve.Entry.State);
        foreach (var ve in eve.ValidationErrors)
        {
            Console.WriteLine("- Property: \"{0}\", Error: \"{1}\"",
                ve.PropertyName, ve.ErrorMessage);
        }
    }
    throw;
}

你也可以在这里查看详细信息

http://mattrandle.me/viewing-entityvalidationerrors-in-visual-studio/ 一个或多个实体验证失败。更多细节请参见'EntityValidationErrors'属性 http://blogs.infosupport.com/improving-dbentityvalidationexception/