asp.net query c# error

Question

I was working with ASP.NET and I try to change a label text and get the value from data base. here is what i do.

First I add database then I create a linq and then I use query to load it but it won't work.

this is query code

protected void Page_Load(object sender, EventArgs e)
{
    DataClasses1DataContext db = new DataClasses1DataContext();
    var q = from dc in db.topboxes
            where dc.id == (1)
            select dc;
    Lmain11.Text = q.ToString();
}

this is image

and this is what I get as label text

SELECT [t0].[id], [t0].[title], [t0].[dc], [t0].[adminid] FROM [dbo].[topbox] AS [t0] WHERE [t0].[id] = @p0

this image

Can someone please tell me what should I do? It is not the value that I indented to print

and also when I want to get dc from database topbox where id = 1 I also try code without () in where line.

also my data is not null

Sebastian Brosch · Accepted Answer · 2017-09-29 16:58:03Z

3

Linq queries return an IEnumerable<T> and you want to access a specific item in the collection, to a specific property. Use FirstOrDefault().

DataClasses1DataContext db = new DataClasses1DataContext();
var q = (from dc in db.topboxes
         where dc.id == 1
         select dc).FirstOrDefault();

Lmain11.Text = q?.SomeProperty;

FirstOrDefault might return default(T) if such was not found in query. In your case the default is null. Use C# 6 ?. operator to safely access the desired property

Using on a linq-2-sql query .ToString() will give you the sql that is being generated - Great when you want to see under the hood :)

edited Sep 29, 2017 at 16:58

Sebastian Brosch

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answered Oct 14, 2016 at 12:53

Gilad Green

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21 Comments

Arsalan Ahmadi Over a year ago

thanks for answer, my data is something else but now it show me a text myprojectname.topbox is what i get.

mason Over a year ago

@ArsalanAhmadi q can be null, if nothing in db.topboxes has an id of 1.

mybirthname Over a year ago

@GiladGreen I didn't think about second execution, now I check the reference code. Thanks +1, I learn something new.

mybirthname Over a year ago

No worries I was going to delete the answer anyway, it was stupid.

Gilad Green Over a year ago

@mybirthname - BTW - awesome picture :P

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