How to get my web service working

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.NET2.0

Hi -

I have a web method calling a stored procedure. The sp works when run separately. Now moving that into the method I am getting a null reference exception which i'm not sure how to resolve. I'm not to familiar with working with service so any help is appreciated. The idea is to select a list of ID's from the sp via the web method. Invoking the web method is when the error is thrown.

Here is the code

<WebMethod()>
Public Function GetPTSID(term As String)
    Dim ptsid As List(Of String)

    Dim cs As String = ConfigurationManager.ConnectionStrings("PTS_EConnectionStringDEV").ConnectionString
    Using con As New SqlConnection(cs)

        Dim cmd As New SqlCommand("stpr_GetPTSIDs", con)
        cmd.CommandType = CommandType.StoredProcedure
        Dim parm As New SqlParameter("term", term)
        cmd.Parameters.Add(parm)
        con.Open()
        Dim reader As SqlDataReader = cmd.ExecuteReader()

        While reader.Read()
            ptsid.Add(reader("TAPV_TAPNUM"))
        End While
    End Using

    Return ptsid

End Function

Posted 30-Jun-15 5:54am

Troy Bryant

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[no name] 30-Jun-15 12:05pm

A null reference where?

Troy Bryant 30-Jun-15 12:07pm

System.NullReferenceException: Object reference not set to an instance of an object.
at ParkerTapWeb.WebService1.GetPTSID(String term) in C:\Users\518563\Documents\ParkerPTSWeb\DAL\WebService1.asmx.vb:line 60

Line 60 which is ptsid.add(reader("tapv_tapnum"))

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Dave Kreskowiak · Accepted Answer · 2015-06-30T06:13:00

Solution 1

The variable you're using to hold your List collection is Nothing (null).

When you declared it like this:

Dim ptsid As List(Of String)

you only said that the variable ptsid CAN hold a List(Of String). You didn't actually create the List.

Change that to

Dim ptsid As New List(Of String)

and you'll create the list.

This one would be really easy to find if you understood how to use the debugger.

Posted 30-Jun-15 6:13am

Dave Kreskowiak

Updated 30-Jun-15 6:16am

v2

Comments

Troy Bryant 30-Jun-15 14:22pm

Unfortunately the first time I ran this with the NEW list it threw this error :

System.InvalidOperationException: There was an error generating the XML document. ---> System.InvalidOperationException: The type System.Collections.Generic.List`1[[System.String, mscorlib, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089]] may not be used in this context.

[no name] 30-Jun-15 15:06pm

I do not believe that is related. That error is probably because you are trying to return a list from a function that is defined as returning nothing.

Dave Kreskowiak 30-Jun-15 15:10pm

OK, that's a different problem. Is this error on the client or the web service code?

Oh, by the way, your function is defined as not returning anything.

My guess is on the client side.

Troy Bryant 30-Jun-15 15:47pm

the issue is on the web service when trying to invoke the method

Dave Kreskowiak 30-Jun-15 16:12pm

Well, then its because your Function declaration doesn't say what it's returning so it returned Nothing (null).

Public Function GetPTSID(term As String) As List(Of String)