save null to sql using Linq to Sql

[mutafa81]

hi have following table student id name school_ID 1 john 5 2 sara 2 3 luije 4 school id name 1 area1 2 area2 3 area3 4 area4 5 area5 need to save "null" to school_ID with student ID(2)..?? thanks in advance

[Mycroft Holmes]

sounds like homework to me - what have you tried so far

Never underestimate the power of human stupidity RAH

[mutafa81]

var q = from d in sdc.student where d.school_ID == 4 select d; q.school_ID = null;

[leppie]

You cant make the primary key NULL!

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[Mirko1980]

In your code, q is not a database row, but the query itself. Also, you are not selecting on student id 2. You should do something like this:

//query for student with id = 2
var q = from d in sdc.student
where d.id == 2
select d;

//getting the first result or null if there is no student
var row = q.FirstOrDefault();

//if there is a result, we update it
if (row != null)
{
row.school_ID = null;
}

//saving changes to DB
sdc.SubmitChanges()

[mutafa81]

ok, got it solve but it is very straing this not work: -------

var q = (from d in sdc.student
where d.id == 2
select d).FirstorDefault();

try {if (q != null) q.school_ID = null;} cathc{ }

------- following works:

int k = 0;
var q = (from d in sdc.student
where d.id == 2
select d).FirstorDefault();
// make exception Division by constant zero
try {if (q != null) k = 1/k;} catch { q.school_ID = null;}

--------------------------- Really don't know why when write this inside catch{} it works if write outside not work Pleae check Thanks

[Mirko1980]

I don't see why this should not work. What you mean by not work? Gives you an error, does nothing or what?