EntityFramework create object

Question

Ladislav, sorry maybe i'm not correctly posed question. Suppose in WinForm application i'm creating new object:

        var newEmission = _emissionBindingSource.Current as Emission;
        if (newEmission == null) return;
        newEmission.SharesNumber = _context.GetNewSharesNumber();

    public int GetNewSharesNumber()
    {
        return Shares.Max(s => s.Number)+1;
    }`

but Max s.Number is not changing untill i havn't saved previous inserted object. So, in this case i must save every object separatly?

UPDATE 1 Suppose i have created new object emission. I took Shares.Max(s => s.Number)+1 to SharesNumber field of new object. Now i want create second emission object, and SharesNumber of this object must be greater to 1 then previous object. I can achieve this only if i save firstly created object.

If this question is only clarification of your first question you should not start a new one but instead modify the old one. — Ladislav Mrnka
– Ladislav Mrnka, Commented May 31, 2011 at 9:08
That needs little bit more explanation to understand what you are trying to do. Generally doing Shares.Max is bad anyway because if your application will be used by multiple users they can create emissions with the same number. — Ladislav Mrnka
– Ladislav Mrnka, Commented May 31, 2011 at 9:10
Ladislav, thank you for your tips. Suppose i have created new object emission. I took Shares.Max(s => s.Number)+1 to SharesNumber field of new object. Now i want create second emission object, and SharesNumber of this object must be greater to 1 then previous object. I can achieve this only if i save firstly created object. — Alex
– Alex, Commented May 31, 2011 at 11:09

Akash Kava · Accepted Answer · 2011-05-31 09:11:28Z

1

    var newEmission = _emissionBindingSource.Current as Emission;
    if (newEmission == null) return;
    newEmission.SharesNumber = _context.GetNewSharesNumber();

public int GetNewSharesNumber()
{
    // this will always query DB for max value
    return Shares.CreateSourceQuery().Max(s => s.Number)+1;
}

But I believe you should use some sort of stored procedure to assign new number or use auto increment column because if you have multiple users using multiple applications, there may be the case of duplicate numbers.

answered May 31, 2011 at 9:11

Akash Kava

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1 Comment

Alex Over a year ago

Sorry, i can't find CreateSourceQuery() method in Shares objectSet.

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