ASP.NET C#: Entity updating is being blocked-CodePudding

Experiencing an issue about updating mysql DB through EF. It's not the first time I'm dealing with it, so I had some ideas about why isn't my data getting changed. I tried changing an element in goods array; tried editing an object, recieved through LINQ-request (seen some examples of this method); made some attempts on marking element found in the database before editing (like EntityState and Attach()). Nothing of these made any difference, so I tried removing <asp:UpdatePanel> from Site.Master to see what happens (responsive for postback blocking to prevent page shaking on update), but nothing changed (while btnRedeemEdit.IsPostBack having its default value).

Code below is the function I use for updates.

protected void btnRedeemEdit_Click(object sender, EventArgs e)
{
    if (!string.IsNullOrEmpty(Request.QueryString["id"]))
    {
        var db = new GoodContext();
        var goods = db.Goods.ToList();
        Good theGood = goods.FirstOrDefault(x => x.Id == int.Parse(Request.QueryString["id"]));
        //db.Goods.Attach(theGood);//No effect
        //db.Entry(theGood).State = System.Data.Entity.EntityState.Modified; //No effect
        if (theGood != default)
        {
            theGood.AmountSold = GetInput().AmountSold;
            theGood.APF = GetInput().APF;
            theGood.Barcode = GetInput().Barcode;
            theGood.Description = GetInput().Description;
            theGood.ImagesUrl = GetInput().ImagesUrl;//"https://i.pinimg.com/564x/2d/b7/d8/2db7d8c53b818ce838ad8bf6a4768c71.jpg";
            theGood.Name = GetInput().Name;
            theGood.OrderPrice = GetInput().OrderPrice;
            theGood.Profit = GetInput().Profit;
            theGood.RecievedOn = GetInput().RecievedOn;//DateTime.Parse(GetInput().RecievedOn).Date.ToString();
            theGood.TotalAmount = GetInput().TotalAmount;
            theGood.WeightKg = GetInput().WeightKg;
            //SetGoodValues(goods[editIndex],GetInput());//Non-working
            db.SaveChanges();
            Response.Redirect("/AdminGoods");
        }
        else Response.Write($"<script>alert('Good on ID does not exist');</script>");
    }
    else Response.Write($"<script>alert('Unable to change: element selected does not exist');</script>");
}

Notice, that no alerts appear during execution, so object in database can be found.

Are there any more things, that can be responsible for blocking database updates?

CodePudding user response：

A few things to update & check:

Firstly, DbContexts should always be disposed, so in your case wrap the DbContext inside a using statement:

using (var db = new GoodContext())
{
    // ...
}

Next, there is no need to load all goods from the DbContext, just use Linq to retrieve the one you want to update:

using (var db = new GoodContext())
{
    Good theGood = db.Goods.SingleOrDefault(x => x.Id == int.Parse(Request.QueryString["id"]));
    if (theGood is null)
    {
        Response.Write($"<script>alert('Good on ID does not exist');</script>");
        return;
    }
}

The plausible suspect is what does "GetInput()" actually do, and have you confirmed that it actually has the changes you want? If GetInput is a method that returns an object containing your changes then it only needs to be called once rather than each time you set a property:

(Inside the using() {} scope...)

var input = GetInput();

theGood.AmountSold = input.AmountSold;
theGood.APF = input.APF;
theGood.Barcode = input.Barcode;
theGood.Description = input.Description;
// ...

db.SaveChanges();

If input has updated values but after calling SaveChanges you aren't seeing updated values in the database then there are two things to check.

1) Check that the database connection string at runtime matches the database that you are checking against. The easiest way to do that is to get the connection string from the DbContext instance's Database.

EF 6:

using (var db = new GoodContext())
{
    var connectionString = db.Database.Connection.ConnectionString; // Breakpoint here and inspect.

EF Core: (5/6)

using (var db = new GoodContext())
{
    var connectionString = db.Database.GetConnectionString();

Often at runtime the DbContext will be initialized with a connection string from a web.config / .exe.config file that you don't expect so you're checking one database expecting changes while the application is using a different database / server. (More common than you'd expect:)

2) Check that you aren't disabling tracking proxies. By default EF will enable change tracking which is how it knows if/when data has changed for SaveChanges to generate SQL statements. Sometimes developers will encounter performance issues and start looking for ways to speed up EF including disabling change tracking on the DbContext. (A fine option for read-only systems, but a pain for read-write)

EF6 & EF Core: (DbContext initialization)

Configuration.AutoDetectChangesEnabled = false; // If you have this set to false consider removing it.

If you must disable change tracking then you have to explicitly set the EntityState of the entity to Modified before calling SaveChanges():

db.Entry(theGood).State = EntityState.Modified;
db.SaveChanges();

Using change tracking is preferable to using EntityState because with change tracking EF will only generate an UPDATE statement if any values have changed, and only for the values that changed. With EntityState.Modified EF will always generate an UPDATE statement for all non-key fields regardless if any of them had actually changed or not.