Left outer join null using VB.NET and LINQ -

Left outer join null using VB.NET and LINQ -

i've got think working left outer bring together linq query, i'm having problems select because of null values in right hand side of join. here have far

dim os = e in oexcel grouping bring together c in oclassindexs on c.tclasscode equals mid(e.classcode, 1, 4) right1 = grouping _ c in right1.defaultifempty

i want homecoming of e , 1 column c called tclasscode. wondering syntax be. can see, i'm using vb.net.

update...

here query doing bring together error:

_message = "object reference not set instance of object."

dim os = e in oexcel grouping bring together c in oclassindexs on c.tclasscode equals mid(e.classcode, 1, 4) right1 = grouping _ c in right1.defaultifempty select e, c.tclasscode

if remove c.tclasscode select, query runs without error. thought perhaps needed select new, don't think doing correctly either.

edit: need check c null, c after grouping. see updates below.

you need null check on tclasscode c in select statement. what type tclasscode? should able null check on the value c , if it's null cast nullable of respective type , returned it, otherwise homecoming actual value.

since not sure tclasscode let's assume it's integer, in case cast nullable integer (integer?). in mind select statement, added @ end of have far, should resemble:

since tclasscode string code resemble:

select _ e, _ code = if(c nothing, nothing, c.tclasscode)

depending on need if c null homecoming string.empty instead of nothing:

select _ e, _ code = if(c nothing, string.empty, c.tclasscode)

of course of study free farther expand selection of "e" project specific columns name.

the of import thing realize must check c null before using of properties since might null depending on left outer bring together result particular result (row). before example, if had field named priority integer cast against nullable:

select _ e, _ priority = if(c nothing, ctype(nothing, integer?), c.priority)

vb.net linq left-join