Calling a C function from C# and getting values from it. - C# Discussion Boards

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Re: Quick quest

musefan30-Jun-09 5:14

musefan

30-Jun-09 5:14

just because you are accessing index 2 of the array it does not mean the length is three. If you can access index 2 without an array then there are at least 3 values.

what you should do is first check the length...

if(array.Length != 3)
  //not correct version request message

then do your switch... I assume that index 3 tells what type of request it is and should always be present?

Life goes very fast. Tomorrow, today is already yesterday.

Filter GridView using a dropdown list but only after page populates with appropriate data from Query String

mjc22530-Jun-09 4:23

mjc225

30-Jun-09 4:23

I am using a GridView on a page that will need to display data based on either a URL passed in with a QueryString OR fields passed from a form. This may return 50-500 records or so based on the state etc... If this is too many, (and only if this is too many) the user will be able to filter based on the occupation. I can get it to filter on query string AND state at the same time but not or sadly. I want it to default to all occupations after pulling from the DB based on state, (I tried setting the default value for occupation to -1) and then, the user can use the dropdown control to filter it more.

<asp:dropdownlist id="ddlCategories" runat="server" appenddatabounditems="True" autopostback="True"
		datasourceid="sdsCategories" datatextfield="Occupation" datavaluefield="Occupation">
			<asp:listitem text="All Categories" value="-1">
		</asp:listitem>
	</asp:dropdownlist>
	<asp:sqldatasource id="sdsCategories" runat="server" connectionstring="<%$ ConnectionStrings:eventsConnectionString1 %>"
		selectcommand="SELECT [Occupation] FROM [Events]" ProviderName="<%$ ConnectionStrings:eventsConnectionString1.ProviderName %>">
	</asp:sqldatasource>


	<asp:gridview id="gvProducts" runat="server" datasourceid="sdsProducts" style="margin-top: 12px;" AllowSorting="True" AutoGenerateColumns="False">
		<columns>
            <asp:BoundField DataField="EventTitle" HeaderText="EventTitle" SortExpression="EventTitle" />
            <asp:BoundField DataField="EventEndDate" HeaderText="EventEndDate" SortExpression="EventEndDate" DataFormatString="{0:MM/dd/yyyy}" />
            <asp:BoundField DataField="EventStartDate" HeaderText="EventStartDate" SortExpression="EventStartDate" DataFormatString="{0:MM/dd/yyyy}" />
            <asp:BoundField DataField="EventCity" HeaderText="EventCity" SortExpression="EventCity" />
            <asp:BoundField DataField="EventState" HeaderText="EventState" SortExpression="EventState" />
            <asp:BoundField DataField="Occupation" HeaderText="Occupation" SortExpression="Occupation" />
		</columns>
	</asp:gridview>
	<asp:sqldatasource id="sdsProducts" runat="server" connectionstring="<%$ ConnectionStrings:eventsConnectionString2 %>"
		selectcommand="SELECT [EventTitle], [EventEndDate], [EventStartDate], [EventCity], [EventState], [Occupation] FROM [Events] WHERE ([EventState] = ?)" ProviderName="<%$ ConnectionStrings:eventsConnectionString2.ProviderName %>">
        <SelectParameters>
            <asp:QueryStringParameter DefaultValue="PA" Name="EventState" QueryStringField="ID"
                Type="String" />
        </SelectParameters>
	</asp:sqldatasource>

complete removing of a C# COM component

manustone30-Jun-09 3:24

manustone

30-Jun-09 3:24

Hi all
maybe you can help me a little bit with COM component developed in C#.

I created one C# COM component to provide Excel with some functionality I needeed.

Everything was fine until I did some change to the assembly.
In the new version I did the following:
-I used the same GUID of the old version
-I used using the same strong key name of the old version
- I changed the Assembly version to 1.0.0.0 to 1.0.0.1.
- I registered the assebly in the global assembly cache with gacutil.

Since then Excel is not able to work anymore with this Com and doesn't recognize the library classes.

I tryed to cleanup of my system so I did:
-removal of the library from the GAC
-removal of the typelib
-reinstall of everything from scratch

at the end nothing improved! Frown | :(

What can I do to a perfect clean up of my system?
Some tool or some registry key or value to see?

Thanks in advance
ManuStone

Combobox and listbox control

Hum Dum30-Jun-09 3:08

Hum Dum

30-Jun-09 3:08

On form load event i am loading dt Datatable obj from DB.

Setting Listbox control dataSource to dt, and respective display member, value member property. But its taking almost 2 sec,

If i do same for combobox control it takes hardly .1 sec

Why this behavior?

Re: Combobox and listbox control

musefan30-Jun-09 3:19

musefan

30-Jun-09 3:19

well it might help to see the code you have used for both methods.

Life goes very fast. Tomorrow, today is already yesterday.

Re: Combobox and listbox control

Hum Dum1-Jul-09 0:04

Hum Dum

1-Jul-09 0:04

musefan wrote:
well it might help to see the code you have used for both method

for combobox

Datatable dt = getTable();
cmb.DataSource = dt;
cmb.DisplayMember = "Name";
cmb.ValueMember = "Level";

for listbox

Datatable dt = getTable();
lst.DataSource = dt;
lst.DisplayMember = "Name";
lst.ValueMember = "Level";

On formLoad event.

this code i used, for cmb its fast, but for listbox its slow,
I am wondering why.........?? Confused | :confused:

i am using c#. vs2003

regards,

Re: Combobox and listbox control

musefan1-Jul-09 1:18

musefan

1-Jul-09 1:18

Sorry, can't really offer a good answer.

To me it looks like you can't really do anything to help it yourself. I'm thinking maybe the comboBox and listBox handle DataSources differently and that is causing the delay - but I don't know that for sure.

Life goes very fast. Tomorrow, today is already yesterday.

Calling a C function from C# and getting values from it.

shivapriyak30-Jun-09 2:42

shivapriyak

30-Jun-09 2:42

I have a C function of format:
func1(double param[], int size);

This function is called from C# code the following syntax:
[DllImport("first.dll", EntryPoint = "func1", CallingConvention = CallingConvention.StdCall)]
public static extern int func1(ref double param[], int size);

The function 'func1' takes two parameters: the array in which values should be filled up from C dll and 'size' which tells the number of values to fill in the array.
Now if the param[] array is declared as param[] = new double[5]; and the 'size' parameter is given as 10, still the function passes.
Wherase the same scenario in direct C application, gives error saying "Array size(i.e. 5) is lesser than the number of values to fill(i.e. 10)".

I am not able to reproduce the same behavior in .Net. Can anybody help me with it?

Re: Calling a C function from C# and getting values from it. [modified]

DaveyM6930-Jun-09 3:26

DaveyM69

30-Jun-09 3:26

~~My guess (I haven't checked) is that the number of bits used in C for the double may be 32, but in C# it's 64.~~

Hmmm, it appears that they are both 8 bytes (64 bit) Confused | :confused:

Dave
BTW, in software, hope and pray is not a viable strategy. (Luc Pattyn)
Visual Basic is not used by normal people so we're not covering it here. (Uncyclopedia)
Why are you using VB6? Do you hate yourself? (Christian Graus)

modified on Tuesday, June 30, 2009 9:36 AM

Re: Calling a C function from C# and getting values from it.

shivapriyak30-Jun-09 3:34

shivapriyak

30-Jun-09 3:34

ok..how to ensure that both the sizes are the same..i mean if i declare array of size 5 (5 x 8 = 40bytes) should be the same in C# also.

Re: Calling a C function from C# and getting values from it.

DaveyM6930-Jun-09 3:39

DaveyM69

30-Jun-09 3:39

I've just edited my previous reply as it appears that double is 8bytes (64 bits) in managed and unmanaged environments Confused | :confused:

Re: Calling a C function from C# and getting values from it.

Luc Pattyn30-Jun-09 4:03

Luc Pattyn

30-Jun-09 4:03

Hi Dave,

native float typically uses 4 bytes, and double doubles that, hence the name.
managed float always uses 4 bytes, and double 8 bytes.

Smile | :)

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DISCLAIMER: this message may have been modified by others; it may no longer reflect what I intended, and may contain bad advice; use at your own risk and with extreme care.

Re: Calling a C function from C# and getting values from it.

Luc Pattyn30-Jun-09 4:09

Luc Pattyn

30-Jun-09 4:09

Hi,

three remarks:

1.

shivapriyak wrote:
public static extern int func1(ref double param[], int size);

I doubt you need the ref there. Objects (array is object) get passed by reference, so what you get is a pointer to the data anyway. With "ref" you get a pointer to a pointer, which you would then have to accept as a double**param.

2.

I typically don't rely on automatics marshaling, instead I use GCHandle class to pin the object and get its pointer into an IntPtr, then pass that to the native world. However, I am not saying your way could not work (without ref!).

3.

shivapriyak wrote:
in direct C application, gives error saying "Array size(i.e. 5) is lesser than the number of values to fill(i.e. 10)".

How the heck can the function now that???

Smile | :)

Luc Pattyn [Forum Guidelines] [My Articles]

DISCLAIMER: this message may have been modified by others; it may no longer reflect what I intended, and may contain bad advice; use at your own risk and with extreme care.

Re: Calling a C function from C# and getting values from it.

shivapriyak30-Jun-09 20:03

shivapriyak

30-Jun-09 20:03

1. I have tried removing 'ref' and giving just double param[] in PInvoke...it didn't work Frown | :(

2. Tried using GCHandle class as below:

int func1(double param[],int size)
{
GCHandle handle = GCHandle.Alloc(param, GCHandleType.Pinned);
Pinvoke.func1(handle.AddrOfPinnedObject(),size);
}
The Pinvoke class is as:
[DllImport("myFile.dll",EntryPoint="func1",CallingConvention = CallingConvention.StdCall)]
public static extern int func1(IntPtr handle, int size);

But it didn't work...is this correct way? or do i need to tweak at some place.

Thanks,
Priya.

Re: Calling a C function from C# and getting values from it.

Luc Pattyn30-Jun-09 22:57

Luc Pattyn

30-Jun-09 22:57

Hi,

shivapriyak wrote:
it didn't work

that does not tell me much

shivapriyak wrote:
int func1(double param[],int size)
{
GCHandle handle = GCHandle.Alloc(param, GCHandleType.Pinned);
Pinvoke.func1(handle.AddrOfPinnedObject(),size);
}

looks good, except when done you need to free the GCHandle.

Smile | :)

Luc Pattyn [Forum Guidelines] [My Articles]

DISCLAIMER: this message may have been modified by others; it may no longer reflect what I intended, and may contain bad advice; use at your own risk and with extreme care.

SQLite in C#

stancrm30-Jun-09 2:35

stancrm

30-Jun-09 2:35

Hello. I'm using SQLite and System.Data.SQLite.
If I create a new table, the file size is 2KB.
After insert 1000 records, the file size will be 34KB.
If I delete all record, the file size remain 34KB.
If I send SELECT command, the table is empty.

Why ?

Thanks.

Re: SQLite in C#

Pete O'Hanlon30-Jun-09 2:39

Pete O'Hanlon

30-Jun-09 2:39

stancrm wrote:
Hello. I'm using SQLite and System.Data.SQLite.
If I create a new table, the file size is 2KB.
After insert 1000 records, the file size will be 34KB.
If I delete all record, the file size remain 34KB.
If I send SELECT command, the table is empty.

Why ?

Because a delete does not reclaim disk space (that would be a very wasteful use of system resources). Databases don't tend to allocate space as records are added, they allocate space in blocks and then insert records to the allocated space (it's much more efficient for them to do this as it results in less I/O activity on the disk).

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Re: SQLite in C#

SeMartens30-Jun-09 2:41

SeMartens

30-Jun-09 2:41

Hi,

you are getting an empty table because you deleted all records before. The file size of the database will not shrink if you delete rows because that would mean a reordering of the internal structure (db-records are stored in pages etc.). Some databases (especially for mobile applications) offer a shrink-command. This will result in the reordering and a smaller file.

At least: Please choose the correct forum for your question, I think "General Database" would be a better place.

Regards
Sebastian

It's not a bug, it's a feature!

Check out my CodeProject article Permission-by-aspect.

Me in Softwareland.

How to Upload large size file to server

wasimsharp30-Jun-09 2:21

wasimsharp

30-Jun-09 2:21

Hi friend i am creating WindowDesktop application that will upload a large size of file to the server.
now when i upload file of small size its uploaded with no problem but when i upload large size of 62Mb or so it throw exception. can any body tell me that how can i upload large file and can i also pause uploading and resume Uploading feature
<pre

filestream="" stream="new" filestream("c:\\xyz.zip",="" filemode.open);

="" byte[]="" buffer="new" byte[stream.length];
="" int="" i="0;
" while="" ((i="stream.Read(buffer,0," buffer.length))>0)
="" {

="" ftpwebrequest="" request="(FtpWebRequest)FtpWebRequest.Create("ftp://ftp.abc.com/"" +="" path.getfilename("c:\\xyz.zip"));
="" try
="" {
="" request.method="WebRequestMethods.Ftp.UploadFile;
" request.credentials="new" networkcredential("demo123",="" "demo123");
="" request.usepassive="true;
" request.usebinary="true;
" request.keepalive="false;
"
="" request.timeout="int.MaxValue;

" reqstream="request.GetRequestStream();
" reqstream.write(buffer,="" 0,="" buffer.length);
="" reqstream.beginwrite(buffer,="" buffer.length,="" callback,="" "aa");
="" reqstream.close();
="" }
="" catch="" (exception="" ex)
="" stream.close();="">

i use both Write and BeginWrite method

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Re: How to Upload large size file to server

Vimalsoft(Pty) Ltd30-Jun-09 2:28

Vimalsoft(Pty) Ltd

30-Jun-09 2:28

We cannot know unless you tell us what Expetion you are getting

Vuyiswa Maseko,

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Re: How to Upload large size file to server

wasimsharp30-Jun-09 2:33

wasimsharp

30-Jun-09 2:33

Hi Vuyiswa Maseko

Error is "Unable to write data to the transport connection: An operation on a socket could not be performed because the system lacked sufficient buffer space or because a queue was full."

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Re: How to Upload large size file to server

Vimalsoft(Pty) Ltd30-Jun-09 2:37

Vimalsoft(Pty) Ltd

30-Jun-09 2:37

musefan is Right increase the Buffer and see what happends