Linq to SQL FirstOrDefault不执行SQL查询

Question

I have a Windows Forms. I instanciate my data context in the form's constructor. I want to display information about article when I click on a button. Data can be updated externally. The problem is that, in this case, data is not refreshed.

I already know that re-instanciate my data context each time is an option. ToList would force to get the refreshed data. But I really thought that FirstOrDefault() would execute SQL each time...

I did some log and this is not the case. Is there an option over there to force the SQL execution? Is there a sort of cache here?

using (var log = new System.IO.StreamWriter("D:\\LOG.TXT", true))
{
    DB.Log = log;

    var article = DB.T_Articles.FirstOrDefault(x => x.NumArticle == 11);
    MessageBox.Show(article.Description);

    var articles = DB.T_Articles.ToList();

    log.WriteLine("----------------------------------");

    DB.Log = null;
}

Here is the log file. We can see that the SQL behind the FirstOrDefault method is here. We can see that it disappears the second time

SELECT TOP (1) [t0].[NumArticle], [t0].[EAN13], [t0].[Minimum], [t0].[Emplacement], [t0].[Fournisseur], [t0].[Qte], [t0].[Description], [t0].[Photo], [t0].[Prix], [t0].[IsEmail]
FROM [dbo].[T_Article] AS [t0]
WHERE [t0].[NumArticle] = @p0
-- @p0: Input Int (Size = -1; Prec = 0; Scale = 0) [11]
-- Context: SqlProvider(Sql2008) Model: AttributedMetaModel Build: 4.7.2046.0

SELECT [t0].[NumArticle], [t0].[EAN13], [t0].[Minimum], [t0].[Emplacement], [t0].[Fournisseur], [t0].[Qte], [t0].[Description], [t0].[Photo], [t0].[Prix], [t0].[IsEmail]
FROM [dbo].[T_Article] AS [t0]
-- Context: SqlProvider(Sql2008) Model: AttributedMetaModel Build: 4.7.2046.0

----------------------------------
SELECT [t0].[NumArticle], [t0].[EAN13], [t0].[Minimum], [t0].[Emplacement], [t0].[Fournisseur], [t0].[Qte], [t0].[Description], [t0].[Photo], [t0].[Prix], [t0].[IsEmail]
FROM [dbo].[T_Article] AS [t0]
-- Context: SqlProvider(Sql2008) Model: AttributedMetaModel Build: 4.7.2046.0

----------------------------------

Answer 1

您可以尝试在FirstOrDefault（）之前每次刷新上下文：

Context.Refresh(RefreshMode.StoreWins, [table_name]);

Answer 2

You can reload the found entry , read more about cache busting

  var article = DB.T_Articles.FirstOrDefault(x => x.NumArticle == 11);
  DB.Entry(article).Reload();