Re: Maching the row in a datagrid to a row in a DataTable - C# Discussion Boards

Re: Maching the row in a datagrid to a row in a DataTable

22-Sep-02 14:02

I have a dataTable set as the Datasource of of a dataGrid via a DataView.

The Table contains an ID field and a Description field, of which only the Description is displayed in the grid.

I want to be able to programatically retrive the ID from the DataTable based on a row in in the DataGrid.

How can I do this, even if the grid has been sorted?

Thanks

Stephen.

Paul Riley22-Sep-02 14:43

Re: Maching the row in a datagrid to a row in a DataTable

22-Sep-02 14:43

If the ID is still bound to a column which is marked as not visible then you should still be able to access it as if it was visible.

Paul

stephen woolhead22-Sep-02 14:48

Re: Maching the row in a datagrid to a row in a DataTable

22-Sep-02 14:48

Thanks for the quick reply, had over looked that simple idea!

Anyway, I would stil like to be able to get back to the row in the dataTable, is it possible?

Thanks

Stephen.

Paul Riley22-Sep-02 14:59

Re: Maching the row in a datagrid to a row in a DataTable

22-Sep-02 14:59

Not sure exactly what you mean. Can you expand on the question a little... give an example if possible.

Paul

stephen woolhead23-Sep-02 0:34

Re: Maching the row in a datagrid to a row in a DataTable

23-Sep-02 0:34

OK, say I had code that looked like this..

DataSet ds = GetMyDataSet () ;<br />
<br />
DataTable dt = ds.Tables["Results"] ;<br />
DataView dv = new DataView (dt) ;<br />
dv.AllowNew = false ;<br />
<br />
dataGrid1.DataSource = dv ;

And somewhere else I want to delete the current row in response to a button click from the tool bar.

I could do..

DataView dv = (DataView )dataGrid1.DataSource ;<br />
DataTable dt = dv.Table ;<br />
dt.Rows[dg.CurrentCell.RowNumber].Delete ;

But if the grid has been sorted by using the column headers this will no longer work as the grid row number no longer matches the row number in the dataTable.

What I would like to do is find a way to go from a row in the datagrid to the row in the datasource.

The delete is just an example, it is the row mapping that is realy of intreast to me.

Thanks

Stephen.

Paul Riley23-Sep-02 1:27

Re: Maching the row in a datagrid to a row in a DataTable

23-Sep-02 1:27

You could search through the DataTable for the record with the same ID column.

But I feel you're missing some of the power of DataSets. Try Adding a DataSet design to your project, define the layout of your dataset and set the ID as a <bold>Primary key.

This generates a DataSet-derived class with a lot more power, exposing methods like Search() or FindByXXX() [where XXX is the Primary Key name].

If you then want to duplicate your changes in some sort of database, take a good look at DataAdapters.

None of this is simple stuff when you first come to look at it but once you've done it a couple of times, you can start knocking them together in no time. Trust me, it's worth the initial effort.

Paul

stephen woolhead23-Sep-02 2:46

Re: Maching the row in a datagrid to a row in a DataTable

23-Sep-02 2:46

I kept the example short in an attempt to get the point of my question cross, is there a way to map the selected row in a datagrid to the related row in the underlying dataset.

I am unable to use DataAdapters as the original datasource is not supported by ADO.NET

I could use the Hidden ID column and search by Primary key method to find the row in the dataset, it just seems wrong when there must be a direct link back to the row in the dataset somewhere. The grid must know what row it is displaying to be able to update when the row is changed!

Also, on a related note, I want to do the same thing in DataGridColumnStyle derived class that uses columns in the DataTable that are not displayed in the grid. In this the edit and comit methods provide a row number in the datagrid, but I am at a loss on how to map that back into the dataset.

Stephen.

Paul Riley23-Sep-02 3:07

Re: Maching the row in a datagrid to a row in a DataTable

23-Sep-02 3:07

stephen woolhead wrote:
I could use the Hidden ID column and search by Primary key method to find the row in the dataset, it just seems wrong when there must be a direct link back to the row in the dataset somewhere.

There isn't, I'm afraid. DataSets and DataGrids are two completely unrelated things, Daatabinding just allows you to link them. You have to create your own link between records like that.

stephen woolhead wrote:
I am unable to use DataAdapters as the original datasource is not supported by ADO.NET

Not even using ODBC.NET[^]?

stephen woolhead wrote:
Also, on a related note, I want to do the same thing in DataGridColumnStyle derived class that uses columns in the DataTable that are not displayed in the grid. In this the edit and comit methods provide a row number in the datagrid, but I am at a loss on how to map that back into the dataset.

Through a primary key again, I suspect. You're stepping a little beyond my range of experience here though Smile | :)

Paul

stephen woolhead23-Sep-02 5:31

Re: Maching the row in a datagrid to a row in a DataTable

23-Sep-02 5:31

Paul Riley wrote:
Not even using ODBC.NET[^]?

I need to access a password protected Paradox table (not by choice Smile | :)

), and as far as I know there is no way to do that with ODBC. So I have a Managed C++ dll that uses the BDE directly to build me a Dataset.

Paul Riley wrote:
stephen woolhead wrote:
I could use the Hidden ID column and search by Primary key method to find the row in the dataset, it just seems wrong when there must be a direct link back to the row in the dataset somewhere.

There isn't, I'm afraid. DataSets and DataGrids are two completely unrelated things, Daatabinding just allows you to link them. You have to create your own link between records like that.

I have fianlly worked it out, looks something like this using the previous delete example...

BindingManagerBase cm = this.BindingContext[dg.DataSource] ;<br />
DataRowView drv = (DataRowView )cm.Current ;<br />
((DataRow )drv.Row).Delete () ;

I found this was a good link if you MSDN installed

ms-help://MS.MSDNQTR.2002APR.1033/vbcon/html/vbconConsumersOfDataOnWindowsForms.htm[^]

While there is no direct link between the dataSet and the DataGrid, there are container level objects that you can access that are looking after it for you.

Anyway, thanks for all your replies, they really helped.

Stephen.

Paul Riley23-Sep-02 5:42

23-Sep-02 5:42

stephen woolhead wrote:
I need to access a password protected Paradox table (not by choice ), and as far as I know there is no way to do that with ODBC.

Ick! No idea, but I suspect you're right.

stephen woolhead wrote:
I have fianlly worked it out ...snip...While there is no direct link between the dataSet and the DataGrid, there are container level objects that you can access that are looking after it for you.

I'm impressed. Didn't know such a thing existed, thanks. Glad to be of some help (if only pointing your mind in the right direction) and it seems I've learned something too Smile | :)

Paul

help

imran_rafique22-Sep-02 13:53

imran_rafique

22-Sep-02 13:53

please read that code and solve my problem.
Given after that code.
///////////////////////////////////////////////////////////
<

public class Win32Hook 
 
{ 
 
     [DllImport("kernel32")] 
 
     public static extern int GetCurrentThreadId(); 
 

 
     [DllImport( "user32", CharSet=CharSet.Auto,CallingConvention=CallingConvention.StdCall)] 
 
     public static extern int SetWindowsHookEx( HookType idHook, 
 
                    HOOKPROC lpfn, 
 
                    int hmod, 
 
                    int dwThreadId 
 
                    ); 
 

 
     public enum HookType 
 
     { 
 
          WH_KEYBOARD = 2 
 
     } 
 
     public delegate int HOOKPROC(int nCode, int wParam, int lParam); 
 

 
     private HOOKPROC hookProc; //private field with class scope 
 

 
     public void SetHook() 
 
     { 
 
           // set the keyboard hook 
 
          hookProc = new HOOKPROC(this.MyKeyboardProc); 
 

 
          SetWindowsHookEx(HookType.WH_KEYBOARD, hookProc, 0,
                    GetCurrentThreadId()); 
 

 
     } 
 

 
     public int MyKeyboardProc(int nCode, int wParam, int lParam) 
 
     { 
 
	  //line of code 

          return 0; 
 
     } 
 
}

To install the hook procedure

Win32Hook hook = new Win32Hook();

hook.SetHook();
///////////////////////////////////////////////////////////

Above code is 100% correct but my problem here is that I want to execute it for each thread for that purpose I modify a line of code and that is
SetWindowsHookEx (HookType.WH_KEYBOARD, hookProc, IntPtr.Zero,0 );

But after changing that line of code it does not solve my problem because MyKeyboardProc function does not execute its code.
I don’t know why? Can any body give its solution?

r00d0034@yahoo.com

Re: help

Stephane Rodriguez.22-Sep-02 20:15

22-Sep-02 20:15

Passing 0 as last parameter value (dwThreadId) complicates a bit things. MSDN says that in this case, the hook procedure must reside in a DLL. See for yourself what's said about lpfn :

lpfn
[in] Pointer to the hook procedure. If the dwThreadId parameter is zero or specifies the identifier of a thread created by a different process, the lpfn parameter must point to a hook procedure in a dynamic-link library (DLL). Otherwise, lpfn can point to a hook procedure in the code associated with the current process.
hMod
[in] Handle to the DLL containing the hook procedure pointed to by the lpfn parameter. The hMod parameter must be set to NULL if the dwThreadId parameter specifies a thread created by the current process and if the hook procedure is within the code associated with the current process.
dwThreadId
[in] Specifies the identifier of the thread with which the hook procedure is to be associated. If this parameter is zero, the hook procedure is associated with all existing threads running in the same desktop as the calling thread.

MS quote (http://www.microsoft.com/ddk) : As of September 30, 2002, the Microsoft® Windows® 2000 DDK, the Microsoft Windows 98 DDK, and the Microsoft Windows NT® 4.0 DDK will no longer be available for purchase or download on this site.

Desktop Hierarchy

Wjousts22-Sep-02 13:41

Wjousts

22-Sep-02 13:41

I'm trying to create a treeview that is populated with the directory structure of the computer (like the left hand window of explorer). I can use System.IO.Directory or System.IO.DirectoryInfo to extract subdirectories for a given root (e.g. C:\) and add them to my tree, but ideally I'd like to start at Desktop and include My Computer (and then A:\,C:\,D:\,etc) just like explorer does. Does the .NET framework have any classes that allow you to move through that hierarchy, i.e. return everything listed under Desktop and then everything under My Computer, etc?
Thanks

Re: Desktop Hierarchy

Paul Riley22-Sep-02 15:07

Dragging files onto a windows form

22-Sep-02 15:07

Check out Environment.GetFolderPath(Environment.SpecialFolder.DesktopFolder).

Paul

help?

imran_rafique22-Sep-02 13:35

imran_rafique

22-Sep-02 13:35

please read that code and solve my problem.
Given after that code.
///////////////////////////////////////////////////////////
>>><<<><

public class Win32Hook  {       [DllImport("kernel32")]       public static extern int GetCurrentThreadId();        [DllImport( "user32", CharSet=CharSet.Auto,CallingConvention=CallingConvention.StdCall)]       public static extern int SetWindowsHookEx( HookType idHook,                      HOOKPROC lpfn,                      int hmod,                      int dwThreadId                      );        public enum HookType       {            WH_KEYBOARD = 2       }       public delegate int HOOKPROC(int nCode, int wParam, int lParam);        private HOOKPROC hookProc; //private field with class scope        public void SetHook()       {             // set the keyboard hook            hookProc = new HOOKPROC(this.MyKeyboardProc);             SetWindowsHookEx(HookType.WH_KEYBOARD, hookProc, 0,                    GetCurrentThreadId());        }        public int MyKeyboardProc(int nCode, int wParam, int lParam)       {  	  //line of code           return 0;       }  }

zimbar22-Sep-02 5:01

zimbar

22-Sep-02 5:01

I'm trying to implement a drag and drop between the windows shell and a windows form but although I implement the drag event nothing happens, when I drag a file. I also cannot find any examples on the topic.

Any ideas?

Re: Dragging files onto a windows form

Stephane Rodriguez.22-Sep-02 5:20

22-Sep-02 5:20

You may look this implementation[^].

Custom Control

Donald Blachly21-Sep-02 18:55

Donald Blachly

21-Sep-02 18:55

I am building a custom control in C# out of existing controls. One question I have:

Normally, when a control such as a TextBox is added to a Form, it is declared as private but as a member of the form, the Textbox.Text for example, is acessible for coding in the form. With a custom control, if I declare the controls as private, they are not directly accessible to the form the control is placed on. Should I declare the individual controls as protected or public members in the custom control and the custom control as private? Will this protect the data members or is the another way that would be better?

When you come to a fork in the road, take it! Y. Berra

Stephane Rodriguez.21-Sep-02 21:24

21-Sep-02 21:24

Adding set/get properties in your custom control allows to inoculate the public interface from the actual custom control implementation. Hence lower code maintenance for instance when a TextBox becomes a MyTextBoxEx.

Of course, no one needs to care that much about object-oriented programming, and the controls could be declared as public. This would btw shorten development time. And there is no need to feel the same for it, especially when things are obvious.

Unfortunately, there is no known option (or I don't know) to tell the VS.NET IDE to add controls as public, instead of private.

My -0.5 cent

James T. Johnson21-Sep-02 21:42

James T. Johnson

21-Sep-02 21:42

StephaneRodriguez wrote:
Unfortunately, there is no known option (or I don't know) to tell the VS.NET IDE to add controls as public, instead of private.

In the properties window there is a property called Modifiers in the Design category; that will let you set the class visibility for the control.

James
"And we are all men; apart from the females." - Colin Davies

Stephane Rodriguez.21-Sep-02 22:59

21-Sep-02 22:59

The Modifiers property applies to an existing control, and on a one-by-one basis. Of course, I admit there is a challenge here for those willing to write the code automating this to the whole set of child controls.(can't figure out by the way why there is no Modifiers property at the Form level, this would have been a nice place for all controls added later).