CODEWITHSUNDEEP
c#linqentity-framework
J.P Masangcay
J.P Masangcay

Reputation: 769

Can't update my db table using Entity Framework and LINQ

I have a database table and I'm trying to update a cell with a money datatype (decimal) and I'm using LINQ and and Entity Framework.

Unfortunately Context.SaveChanges(); won't work for some reason.

Here is the table structure

Type Amount Machine
Cash 1000   Tablet

Here is my code:

using (var GC = new GroundCommanderEntities())
{
    PAYMENT_Repo PAYMENTREPO = new PAYMENT_Repo(); 
    var ExistingCashPayment = GC.PAYMENT_Repo
        .Where(Filter => Filter.Type == "Cash" && Filter.Machine == "Tablet").ToList();

    string type = "";
    var amt = 0.00m;

    foreach (var item in ExistingCashPayment)
    {
        type = item.Type;
        amt = item.Amount;
    }

    if (type == cbPaymentType.Text) //a combobox that contains Types 
    {
        PAYMENTREPO.Amount = amt + Convert.ToDecimal(txtTendering.Text);                    
        GC.SaveChanges();

        return true;
     }
     else
     {
         return false;
     }             
}

Upvotes: 1

Views: 687

Answers (3)

Anis Sivasankaran
Anis Sivasankaran

Reputation: 21

It looks like GC is your DbContext. If so you need to add the state of the object is modified as follows...

db.Entry(obj).State = System.Data.Entity.EntityState.Modified; db.SaveChanges();

This should work.

Upvotes: 2

Jon Egerton
Jon Egerton

Reputation: 41539

There are a couple of problems here:

Most importantly, PAYMENTREPO is a new instance - its not from the db context, so changing values on it has no effect. You need to add it before saving changes:

PAYMENTREPO.Amount = amt + Convert.ToDecimal(txtTendering.Text);                    
GC.PAYMENTREPOs.Add(PAYMENTREPO);
GC.SaveChanges();

Second, which won't cause the complete fail to update, but will cause the code to do things other than you expect:

foreach (var item in ExistingCashPayment)
{
    type = item.Type;
    amt = item.Amount;
}

This loop will leave type and amt set to the last value in the ExistingCashPayment list, rather than some sort of accumulation of the contents of that list, which would be the desired behaviour implied by having the loop there in the first place.

Upvotes: 1

marc_s
marc_s

Reputation: 754220

When you create a new entity like you do, you must add it to the context before calling SaveChanges():

using (var GC = new GroundCommanderEntities())
{
    PAYMENT_Repo PAYMENTREPO = new PAYMENT_Repo(); 
    var ExistingCashPayment = GC.PAYMENT_Repo
        .Where(Filter => Filter.Type == "Cash" && Filter.Machine == "Tablet").ToList();

    string type = "";
    var amt = 0.00m;

    foreach (var item in ExistingCashPayment)
    {
        type = item.Type;
        amt = item.Amount;
    }

    if (type == cbPaymentType.Text) //a combobox that contains Types 
    {
        PAYMENTREPO.Amount = amt + Convert.ToDecimal(txtTendering.Text);                    

        // add your NEW entity to the context!
        // depending on which exact version of EF you're using, this
        // might be called `.Add()` or `.AddObject()`
        // Also, the name "PAYMENTREPOs" is just a guess - it might be 
        // different in your concrete case - adapt as needed!
        GC.PAYMENTREPOs.Add(PAYMENTREPO);

        GC.SaveChanges();

        return true;
     }
     else
     {
         return false;
     }             
}

Upvotes: 1

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