(0xc0000005) 'Access violation': LINQ to SQL WPF VB.NET -

application compiles no errors. application runs ends no debug errors. stepping through it, cuts designer @ line output showing:

"the program '[24680] appname.vshost.exe' has exited code -1073741819 (0xc0000005) 'access violation'." 

crashes on line:

dim c_instancedetail t_instance_detail = (from instdet in db.t_instance_details instdet.id = guinstance_id select instdet).single 

in sub:

private sub refresh_pca_instancedetail()     dim c_instancedetail t_instance_detail = (from instdet in db.t_instance_details instdet.id = guinstance_id select instdet).single      me.datacontext = c_instancedetail     me.instancedetailtypeview = ctype(collectionviewsource.getdefaultview(me.datacontext), bindinglistcollectionview) end sub 

edit: class variables:

private db new appdatabase_dbdatacontext 'appdatabase_db being name of dbml file - appdatabase_db.dbml private instancedetailtypeview bindinglistcollectionview property guinstance_id guid 

t_instance_detail created linq sql classes , i've tried removing , re-adding - no change

this works (and returns 1 record):

dim c_instancedetail = (from instdet in db.t_instance_details instdet.id = guinstance_id select instdet) 

i'm new linq sql , wpf, i'm assuming i'm doing wrong or using linq sql classes in why unintended. if can let me know i'm doing wrong here, , how should doing this, great thanks.

i think issue possibility of not returning record (even though returning 1 record @ point in time). below fixed it:

private sub refresh_pca_instance()     dim c_instance ienumerable(of t_instance)     c_instance = (from inst in db.t_instances inst.id = guinstance_id select inst)      if c_instance.count = 1         me.datacontext = c_instance         me.instancedetailtypeview = ctype(collectionviewsource.getdefaultview(me.datacontext), bindinglistcollectionview)     elseif c_instance.count > 1         me.datacontext = c_instance.first         me.instancedetailtypeview = ctype(collectionviewsource.getdefaultview(me.datacontext), bindinglistcollectionview)     end if end sub 

edit: more this, find better/other ways:

private sub refresh_pca_instance()     dim c_instance ienumerable(of t_instance)     c_instance = (from inst in db.t_instances inst.id = guinstance_id select inst).first      me.datacontext = c_instance     me.instancedetailtypeview = ctype(collectionviewsource.getdefaultview(me.datacontext), bindinglistcollectionview) end sub 

or

private sub refresh_pca_instance()     dim c_instance ienumerable(of t_instance)     c_instance = (from inst in db.t_instances inst.id = guinstance_id select inst)      me.datacontext = c_instance.first     me.instancedetailtypeview = ctype(collectionviewsource.getdefaultview(me.datacontext), bindinglistcollectionview) end sub