Linq Query is causing error when trying to retrieve from database

Question

I've tried the below query to get a list from a database using linq but get the following error

Unable to create a constant value of type 'System.Object'. Only primitive types or enumeration types are supported in this context.

I'm not sure why the error is being caused.

 List<a> a = await (from p in new db_Context().Items
                    where p.sub_Var.Name.Equals((sender as Button).Text)
                    orderby p.Name
                    select p).ToListAsync();

make sure your sender actually is a Button Object every time this function gets called other than this I dont see where a null reference might comw from — D4rth B4n3, Oct 22 '17 at 16:36

Sajeetharan · Answer 1 · 2017-10-22T16:45:39.937

1

use == instead of Equals

 List<a> a = await (from p in new db_Context().Items
                    where p.sub_Var.Name == ((sender as Button).Text)
                    orderby p.Name
                    select p).ToListAsync();

EDIT

if you are getting null, set the button text to a variable and check ,

string buttonname = (sender as Button).Text;


List<a> a = await (from p in new db_Context().Items
                        where p.sub_Var.Name == buttonname 
                        orderby p.Name
                        select p).ToListAsync();

edited Oct 22 '17 at 16:45

answered Oct 22 '17 at 16:22

Sajeetharan

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I'm now getting, "Object reference not set to an instance of an object.'. Any ideas and nothing appears to be null – Max Oct 22 '17 at 16:27
you need another ( , check the updated answer – Sajeetharan Oct 22 '17 at 16:28
did it work for you – Sajeetharan Oct 22 '17 at 16:40
Hi the answer was to set it to a variable first, thanks for the help – Max Oct 22 '17 at 16:43

score 0 · Accepted Answer · answered Oct 22 '17 at 16:36

0

string name = (sender as Button).Text;

List<a> a = await (from p in new db_Context().Items
                    where p.sub_Var.Name == name 
                    orderby p.Name
                    select p).ToListAsync();

answered Oct 22 '17 at 16:36

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Linq Query is causing error when trying to retrieve from database

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