help! set selected items in listbox selected from database items

[dzr]

I have an array of numbers 3,6,10,15 and they print just fine in a loop but when I try to set the multiselect items they match, I get a "Object reference instance of an object." error.


html output:

<select size="4" name="jobtypes" multiple="multiple" id="jobtypes">
<option value="1">Teacher</option>
<option value="2">Nurse</option>
<option value="3">Fireman</option>
<option value="4">Waitress</option>
...
</select>

codebehind:

foreach (string s in jobtitles)
{
jobtitles.Items.FindByValue(s).Selected = true;

}

Any input would be greatly appreciated!!!

 

[xcalibre]

Just out of curiosity... is your codebehind supposed to reference "jobtypes" or "jobtitles"?

 

[dzr]

job types is the array of job titles a user has selected - comma delimited, coming from the DB and split up into just number values. Field is nvarchar in the DB.

all the examples on the web are from post-back forms so i couldn't figure out if i needed to loop through the multi-select items and have a loop inside that loop comparing it with the db values??

anyone have an example?

thanks!

 

[dzr]

there were some typos in my above post... this is more clear:

everything below works as expected until #6 where I try to have the multi-select listbox display the selected items in an edit form.

1. form code --i'm populating the listbox with items from the 'jobs' table using a select statment

<td align="right" valign="top">*Community Jobs Available</td>
<td valign="middle" style="width: 323px"><asp:ListBox ID="choosejobs" runat="server" DataSourceID="SqlDataSource1"
DataTextField="job_title" DataValueField="job_id" SelectionMode="Multiple" ></asp:ListBox>
<asp:SqlDataSource ID="SqlDataSource1" runat="server" ConnectionString="<%$ ConnectionStrings:myConnectionString %>"
SelectCommand="SELECT * FROM [jobs] WHERE ([job_location] = @job_location)">
<SelectParameters>
<asparameter DefaultValue="San Francisco" Name="job_location" Type="String" />
</SelectParameters>
</asp:SqlDataSource>
</td>

2. form code rendered in browser:
<select size="4" name="choosejobs" multiple="multiple" id="choosejobs">
<option value="1">Teacher</option>
<option value="2">Nurse</option>
<option value="3">Fireman</option>
<option value="4">Waitress</option>
<option value="4">Doctor</option>
...
</select>


3. when submitted - i turn it into a comma delimted set of job_id's like this--> 2,5,6 and write to a db record for the user

4. exact same set up as #1 for up edit form
[the edit form is in a seperate location (only available to Admin and has some extra fields)]

5. select * from user_jobs -- get user's list of jobs
string userjobs = dbreader["userjobs"] --> which makes userjobs = "1,2,5"
turn into array of string values (this works fine - I have printed it to the screen and all values are coming out ok)

6. loop through that array to set selected
foreach (string j in userjobs)
{
choosejobs.Items.FindByValue[j].Selected = true;
}

7. error! "System.NullReferenceException: Object reference not set to an instance of an object."


i have tried this: choosejobs.Items.FindByValue("3").Selected = true;
and get the same error so I think I'm something wrong in calling the Items.FindByValue ??

i would appreciate any help please!

 

[tcstom]

Looks like there comes a point when choosejobs.Items.FindByValue[j] does not reference an item i.e. no item has the value j. You could do...

if (choosejobs.Items.FindByValue[j] != null)
{
  choosejobs.Items.FindByValue[j].Selected = true;
}

...or use try/catch....

Tom