使用DBContext Entry.OriginalValues和Entry.NewValues记录更改的值 [英] Recording changed values with DBContext Entry.OriginalValues and Entry.NewValues

问题描述

我有一个文档库网站，并希望在编辑文档对象时发送电子邮件，其中包含更改的摘要。

I have a document library site and would like to send an email when a document object is edited, containing a summary of the changes.

数据库交互是代码使用DBContext的第一个实体框架

The database interaction is Code First Entities Framework using DBContext

这是我迄今为止所做的：

Here is what I have so far:

    [HttpPost]
    public ActionResult Edit(Document document, bool sendEmail, string commentsTextBox)
    {

        if (ModelState.IsValid)
        {
            docsDB.Entry(document).State = EntityState.Modified;

            foreach (string propertyName in docsDB.Entry(document).OriginalValues.PropertyNames)
            {
                var OriginalValue = docsDB.Entry(document).OriginalValues.GetValue<object>(propertyName);
                var NewValue = docsDB.Entry(document).CurrentValues.GetValue<object>(propertyName);
                if (!OriginalValue.Equals(NewValue))
                {
                    //capture the changes
                }
            }

            docsDB.SaveChanges();
            if (sendEmail)
            {
               //sends email
            }
            return RedirectToAction("Index");

        }

然而，OriginalValue和NewValue总是相同的 -

However, OriginalValue and NewValue are always the same -- the values of the update.

有没有什么办法，比如写入文件的东西比较麻烦，在POST之前捕获文档的状态？

Is there any way, short of something hacky like writing to a file, to capture the state of the document before the POST?

推荐答案

要将更新的属性与数据库中的值进行比较，必须从数据库重新加载文档。您可以这样尝试：

For the comparison of the updated properties with the values in the database you must reload the document from the database. You can try it this way:

[HttpPost]
public ActionResult Edit(Document document, bool sendEmail,
    string commentsTextBox)
{
    if (ModelState.IsValid)
    {
        var documentInDB = docsDB.Documents.Single(d => d.Id == document.Id);

        docsDB.Entry(documentInDB).CurrentValues.SetValues(document);

        foreach (string propertyName in docsDB.Entry(documentInDB)
                                        .OriginalValues.PropertyNames)
        {
            var OriginalValue = docsDB.Entry(documentInDB)
                                .OriginalValues.GetValue<object>(propertyName);
            var NewValue = docsDB.Entry(documentInDB)
                           .CurrentValues.GetValue<object>(propertyName);

            if (!OriginalValue.Equals(NewValue))
            {
                //capture the changes
            }
        }

        docsDB.SaveChanges();
        if (sendEmail)
        {
           //sends email
        }
        return RedirectToAction("Index");
    }
    // ...
}

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