c# - SELECT @@IDENTITY giving Specified Cast is not Valid? -


this question has answer here:

hope can this

i trying insert row of data table [issues] guid id column of issues can inserted table actions, creating link between two. relationship [issues]one many[actions].

when run code causes specified cast not valid error here: guid lastid = (guid)sel.executescalar();

lastid variable want assign last guid created can passed table insert table actions.

if can great! thanks

i using c# 2010 express

//this declared @ top of form public guid lastid;          private void pbsaveissue_click(object sender, eventargs e)         {         sqlceconnection arcbaseconn = new sqlceconnection(@"data source=|datadirectory|\arcbase.sdf");          try         {             string cmdissuesubmit = "insert issues (type,description,dateraised,site,reportedby,status) values (@type,@description,@dateraised,@site,@reportedby,@status)";             string typesubmit = cbissuetype.text;             string descriptionsubmit = rtbdescription.text;             string sitesubmit = cbissuesite.text;             string reportedbysubmit = cbreportedby.text;             string dateraisedsubmit = dtpdateraised.text;              sqlcecommand sel = new sqlcecommand();             sel.connection = arcbaseconn;             sel.commandtype = commandtype.text;             sel.commandtext = cmdissuesubmit;             sel.parameters.addwithvalue("@type", typesubmit);             sel.parameters.addwithvalue("@description", descriptionsubmit);             sel.parameters.addwithvalue("@dateraised", dateraisedsubmit);             sel.parameters.addwithvalue("@site", sitesubmit);             sel.parameters.addwithvalue("@reportedby", reportedbysubmit);             sel.parameters.addwithvalue("@status", lbstatus.text);              arcbaseconn.open();             sel.executenonquery();               //here problem              // grab last unique id issue entered , assign variable can entered actions below.             string cmdgetlastid = "select @@identity";             sel.commandtext=cmdgetlastid;              guid lastid = (guid)sel.executescalar();             arcbaseconn.close();         }         catch (sqlceexception ex)         {             messagebox.show(ex.message, application.productname, messageboxbuttons.ok, messageboxicon.error);             application.exitthread();         }

assuming table inserting has identity column defined,

  • identity columns must integer types (tinyint, smallint, int or bigint), not guid, casting guid won't work (as discovered).
  • you want use @@scope_identity instead of @@identity, lest discover pain caused race conditions.

from looks of code, aren't doing this, but...

if trying value of column defined uniqueid (and don't have race condition), need this:

declare @my_guid uniqueid = newid()  insert issues (   type        ,   description ,   dateraised  ,   site        ,   reportedby  ,   status       ,   unique_guid_column ) values (   @type        ,   @description ,   @dateraised  ,   @site        ,   @reportedby  ,   @status      ,   @my_guid )  select case @@error when 0 @myguid else null end

and execute using executescalar().


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