如何在C＃中的foreach循環中實例化並添加到類

Question

我有要用於記錄錯誤消息的代碼。 我制作了兩個這樣的類來保存消息：

public class HttpStatusErrors
{
    public HttpStatusErrors()
    {
        this.Details = new List<HttpStatusErrorDetails>();
    }
    public string Header { set; get; }
    public IList<HttpStatusErrorDetails> Details { set; get; }
}
public class HttpStatusErrorDetails
{
    public HttpStatusErrorDetails()
    {
        this.Details = new List<string>();
    }
    public string Header { set; get; }
    public IList<string> Details { set; get; }
}

我認為這是執行此操作的好方法，但是我不確定100％會接受任何建議。

我想在第一類中存儲Header ，在我的示例中為“ Validation Messages”。 然后在Detail對象中，我想存儲另一個Header ，該Header顯示有錯誤的實體，最后在Details存儲驗證錯誤。

我很困惑的是我應該如何實例化這些類。 到目前為止，我已經做到了。 我認為這是正確的。 但是如何添加需要添加的詳細信息：

catch (DbEntityValidationException ex)
{
    var msg = new HttpStatusErrors();
    msg.Header = "Validation Error";

    foreach (var eve in ex.EntityValidationErrors)
    {
        var header = string.Format("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)
        {
            var detail = string.Format("- Property: \"{0}\", Error: \"{1}\"",
                ve.PropertyName, ve.ErrorMessage);
        }

    }

}.

Answer 1

在“ Details屬性中實例化集合。 實例化新項目，並將其添加到循環中的集合中：

var msg = new HttpStatusErrors();
msg.Header = "Validation Error";
msg.Details = new List<HttpStatusErrorDetails>();

foreach (var eve in ex.EntityValidationErrors)
{
    var detail = new HttpStatusErrorDetails()
    detail.Header = String.Format("Entity of type \"{0}\" in state \"{1}\" has the following validation errors:",
        eve.Entry.Entity.GetType().Name, eve.Entry.State);

    detail.Details = new List<string>();
    foreach (var ve in eve.ValidationErrors)
    {
        detail.Details.Add(String.Format("- Property: \"{0}\", Error: \"{1}\"",
            ve.PropertyName, ve.ErrorMessage));
    }

    msg.Details.Add(detail);
}

順便說一句，您可以為此使用LINQ：

var msg = new HttpStatusErrors();
msg.Header = "Validation Error";
msg.Details =
    ex.EntityValidationErrors
      .Select(eve => new HttpStatusErrorDetails {
                Header = String.Format("Entity of type \"{0}\" in state \"{1}\" has the following validation errors:", eve.Entry.Entity.GetType().Name, eve.Entry.State)
                Details = eve.ValidationErrors
                         .Select(ve => String.Format("- Property: \"{0}\", Error: \"{1}\"", ve.PropertyName, ve.ErrorMessage))
                         .ToList()
       }).ToList();

---

我也喜歡擴展方法語法：

 public static HttpStatusErrors ToHttpStatusErrors(
      this DbEntityValidationException ex)
 {
      return new HttpStatusErrors {
          Header = "Validation Error",
          Details = ex.EntityValidationErrors
                      .Select(eve => eve.ToHttpStatusErrorDetails())
                      .ToList()
      };
 }

 public static HttpStatusErrorDetails ToHttpStatusErrorDetails(
      this DbEntityValidationResult eve)
 {
      return new HttpStatusErrorDetails {
        Header = String.Format("Entity of type \"{0}\" in state \"{1}\" has the following validation errors:",
                               eve.Entry.Entity.GetType().Name, eve.Entry.State),
        Details = eve.ValidationErrors
                     .Select(ve => ve.ToErrorDescription())
                     .ToList()
      };
 }

 public static string ToErrorDescription(
      this DbValidationError ve)
 {
      return String.Format("- Property: \"{0}\", Error: \"{1}\"",
                           ve.PropertyName, ve.ErrorMessage);
 }

此類方法的用法如下：

catch (DbEntityValidationException ex)
{
    var msg = ex.ToHttpStatusErrors();
}

Answer 2

請嘗試以下操作：

foreach (var eve in ex.EntityValidationErrors)
{
    //New Details Entity
    var errorDetail = new HttpStatusErrorDetails();

    //Fill in Header
    errorDetail.Header = string.Format("Entity of type \"{0}\" in state \"{1}\" has the following validation errors:",
        eve.Entry.Entity.GetType().Name, eve.Entry.State);

    //Fill Add a detail for each validation error
    foreach (var ve in eve.ValidationErrors)
    {
        errorDetail.Details.Add(string.Format("- Property: \"{0}\", Error: \"{1}\"",
            ve.PropertyName, ve.ErrorMessage));
    }

    //Add Detail to header
    msg.Details.Add(errorDetail);
}