problem using dataRelation in dot net - C# Discussion Boards

How to get signal strength of multi-AP from wireless net card using c#

pandazhao28-Jul-10 9:27

28-Jul-10 9:27

question description:
I want to use notebook with a wireless netcard to acquire more than 3 Access Pionts(wireless router) signal strength. And using the GPSlike method to measure the position of the laptop.But I don't know how to get all the signal strength. When I use the class Atheros5000_80211_ReceivedSignalStrength of WMI, I can get only ONE singal strength with its property "Ndis80211ReceivedSignalStrength".And what should I do? I am puzzled.

PS:I am a beginner, and English is not my mother tongue, so please do not use too much Abbreviation,thank you very much.

Re: How to get signal strength of multi-AP from wireless net card using c#

Roger Wright28-Jul-10 20:03

Roger Wright

28-Jul-10 20:03

I'm not familiar with the Atheros class, but I know what you mean, I think. A wireless adapter in Windows can report multiple access points in range, and Windows can display all of them to let you choose which to connect to. So there must be a way to get this information from the adapter. It sounds like there should be an enumeration you can cycle through to find all detected stations and return their respective signal strengths. Since I don't know how to do that, I can only recommend that you dig more deeply into the WMI documentation, and try Google for "enumerating wireless access points" or some similar term. Perhaps my rewording of things will trigger some responses from more knowledgeable people - I hope so, as it sounds like an interesting problem.

"A Journey of a Thousand Rest Stops Begins with a Single Movement"

Re: How to get signal strength of multi-AP from wireless net card using c#

pandazhao29-Jul-10 1:32

pandazhao

29-Jul-10 1:32

Thank you very much! Enumerating SSID is very easy because there is a special class in WMI to get SSID, but I don't know how to get the corresponding signal strength.I'v searched for these key words,but got nothing. And I am trying to use DeviceIOControl() to get all the signals. Or DLLImport some exist VC++ dll file instead.

Message Removed

28-Jul-10 5:57

alleyes

28-Jul-10 5:57

Message Removed

Re: Using assembly information from a different assembly

William Winner28-Jul-10 10:37

William Winner

28-Jul-10 10:37

I know this was answered in Quick Answer, but an FYI.

One, don't cross-post. By that I mean, post your question in one place and wait for an answer, not in two or more forums.

Secondly, if you solve your problem in one of these forums (not the quick answers) then edit the title so that it says solved.

Re: Using assembly information from a different assembly

alleyes28-Jul-10 10:56

alleyes

28-Jul-10 10:56

If I could have withdrawn from quick answer I would have so as to not double post. As it was I got my answer in the Quick Answer. So better that it remained there for visibility.

Re: Using assembly information from a different assembly

Pete O'Hanlon28-Jul-10 19:24

Pete O'Hanlon

28-Jul-10 19:24

As you had a reply to your message here, you would have been better editing your question to put a link to the QA version. As it is, there's now a dangling reply.

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problem using dataRelation in dot net

Dhyanga28-Jul-10 4:17

Dhyanga

28-Jul-10 4:17

I have been trying to solve the problem related with using dataRelation but still couldn't figure it out. I hope somebody can help me with this.

I have two repeaters used one nested another.
part of code is shown below:

void Repeater1_ItemDataBound(object sender, RepeaterItemEventArgs e)
       {
           RepeaterItem item = e.Item;
           if ((item.ItemType == ListItemType.Item) ||
               (item.ItemType == ListItemType.AlternatingItem))
           {

               Repeater2 = (Repeater)e.Item.FindControl("Repeater2");
               DataRowView drv = (DataRowView)item.DataItem;
               Repeater2.DataSource = drv.CreateChildView("categoryItem");
               Repeater2.DataBind();
           }
       }

This categoryItem is from this code:

objDA.Fill(ds);
            DataColumn c1 = ds.Tables["category"].Columns["ID"];
            DataColumn c2 = ds.Tables["Item"].Columns["catID"];
            dRel = new DataRelation("categoryItem", c1, c2);
            ds.Relations.Add(dRel);
            Repeater1.DataSource = ds;
            Repeater1.DataBind();

And the error message is:

 Object reference not set to an instance of an object.
Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details: System.NullReferenceException: Object reference not set to an instance of an object.

Source Error:

Line 1222:            objDA.Fill(ds);
Line 1223:
Line 1224:            DataColumn c1 = ds.Tables["category"].Columns["ID"];
Line 1225:            DataColumn c2 = ds.Tables["item"].Columns["catID"];
Line 1226:            dRel = new DataRelation("categoryItem", c1, c2);

Well the "ID" of table "category" is the foreign key in "item" table and that foreignKey name in the "item" table is "catID".

Any help will be appreciated..

I really need some help in this.

suchita

Re: problem using dataRelation in dot net

freakyit28-Jul-10 4:26

freakyit

28-Jul-10 4:26

Line 1222: objDA.Fill(ds);

may objDA is null or ds ^^

Re: problem using dataRelation in dot net

Dhyanga28-Jul-10 4:28

Dhyanga

28-Jul-10 4:28

thanks for the reply .

ds is not null. If i show the values of ds in datagrid, all those data is shown with no problem..

Grid1.DataSource = ds;
Grid1.DataBind();

the above code is running well.

error is showing on the line 1224 .. Frown | :(

suchita

Re: problem using dataRelation in dot net

freakyit28-Jul-10 4:30

freakyit

28-Jul-10 4:30

than objDA will be null the exception is NullReferenceException that implicit says that one object is null at the run time set breakpoints and check if all vars you use are not null.

bless

Re: problem using dataRelation in dot net

Dhyanga28-Jul-10 4:34

Dhyanga

28-Jul-10 4:34

thanks for the reply again.
it is showing error in line 1224 but since my ds has all the data , i dont know why the error in this line ?

suchita

Re: problem using dataRelation in dot net

Eddy Vluggen28-Jul-10 5:03

Eddy Vluggen

28-Jul-10 5:03

Line 1224 consists of multiple statements:

Line 1224:            DataColumn c1 = ds.Tables["category"].Columns["ID"];

I suggest you cut it up into multiple lines, with a breakpoint on each line.
What does ds.Tables["category"] evaluate to? Does that new object have a column labeled "ID"?

SayamiSuchi wrote:
i dont know why the error in this line ?

One of those statements on that line evaluates to null.

I are Troll Suspicious | :suss:

Re: problem using dataRelation in dot net

Eddy Vluggen28-Jul-10 5:13

Eddy Vluggen

28-Jul-10 5:13

You're having trouble debugging?

Start here[^] in order to learn how to inspect those values.

I are Troll Suspicious | :suss:

Re: problem using dataRelation in dot net

Dhyanga28-Jul-10 5:38

Dhyanga

28-Jul-10 5:38

thank you

suchita

Re: problem using dataRelation in dot net

Luc Pattyn28-Jul-10 5:00

Luc Pattyn

28-Jul-10 5:00

objDA is probably null

Hmmm | :|

Luc Pattyn [Forum Guidelines] [Why QA sucks] [My Articles] Nil Volentibus Arduum

Please use <PRE> tags for code snippets, they preserve indentation, and improve readability.

Re: problem using dataRelation in dot net

Dhyanga28-Jul-10 5:08

Dhyanga

28-Jul-10 5:08

objDA is filling ds. ds is getting value.. isn't that means objDA has value ?? Or is there anyway to check the data inside objDA?

Thanks,
suchita

Re: problem using dataRelation in dot net

Luc Pattyn28-Jul-10 5:22

Luc Pattyn

28-Jul-10 5:22

I can't tell what is wrong by seeing only some part of the relevant code.
if you think everything is correct, how come the exception?

now replace

objDA.Fill(ds);
...

try {
    if (objDA==null) MessageBox.Show("Oh dear, objDA seems to be null");
    objDA.Fill(ds);
    ...
} catch(Exception exc) {
    MessageBox.Show("exception: "+exc.ToString());
}

Luc Pattyn [Forum Guidelines] [Why QA sucks] [My Articles] Nil Volentibus Arduum

Please use <PRE> tags for code snippets, they preserve indentation, and improve readability.

Re: problem using dataRelation in dot net

Richard Blythe28-Jul-10 5:26

Richard Blythe

28-Jul-10 5:26

Don't take it personal SayamiSuchi. Luc is not partial to any codeproject member. He gripes at all of us! Big Grin | :-D

The mind is like a parachute. It doesn’t work unless it’s open.

Re: problem using dataRelation in dot net

Luc Pattyn28-Jul-10 5:47

Luc Pattyn

28-Jul-10 5:47

You know pretty well an open mind is the numero uno prerequisite when debugging some code...

Smile | :)

Luc Pattyn [Forum Guidelines] [Why QA sucks] [My Articles] Nil Volentibus Arduum

Please use <PRE> tags for code snippets, they preserve indentation, and improve readability.

Re: problem using dataRelation in dot net

Dhyanga28-Jul-10 5:27

Dhyanga

28-Jul-10 5:27

Thank you for the reply.

my code

DataColumn c1 = ds.Tables["category"].Columns["ID"];

is throwing that error. but since my dataset has values, i dont know how come that error ?

suchita

Re: problem using dataRelation in dot net

Richard Blythe28-Jul-10 5:41

Richard Blythe

28-Jul-10 5:41

When I use a DataAdapter to fill a DataTable, I have to manually set the DataTable's name.
If the same logic applies, You may need to manually set the names of your DataSet tables.

The mind is like a parachute. It doesn’t work unless it’s open.

Re: problem using dataRelation in dot net

Dhyanga28-Jul-10 5:44

Dhyanga

28-Jul-10 5:44

ok. But since i'm using join of two tables, how i'm gonna give two tables name in there ? Or is it just whatever name I'm giving for the dataset ?

suchita

Re: problem using dataRelation in dot net

Richard Blythe28-Jul-10 5:54

Richard Blythe

28-Jul-10 5:54

What is your SELECT query for your data adapter?

The mind is like a parachute. It doesn’t work unless it’s open.

Re: problem using dataRelation in dot net

Dhyanga28-Jul-10 6:22

Dhyanga

28-Jul-10 6:22

select i.ID,j.Item,j.catID from category i, item j where i.ID = j.catID

suchita

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