Extending a Collection indexer

[Matt]

Hi,

I've been thinking about how to do this, but can't think of a solution.

I have a class that is derived from System.Web.UI.W ebControls.Data Grid which
works a treat, but I'd like to extend the DataGridColumnC ollection class
(property of DataGrid) just a fraction by allowing a string indexer. i.e.
rather than using

myDataGrid.Colu mns[7].Visible = false;

I'd like to be able to do this:

myDataGrid.Colu mns["Balance"].Visible = false;

Background: We have a design where only certain columns are shown depending
on the currently logged in user's roles. Management tend to keep changing
the layout by moving columns around, creating havoc in the code behind as
hiding/showing columns is currently done by using the indexer as shown
above. Moving column 7 to column 9 causes problems if you forget to change
the role checks for columns above 8 etc. I've introduced int constants now
for column names to help a bit, but still can create problems if not done
correctly. It would be nicer to use "Key" names. All columns of myDataGrid
derive from their parent (eg myNamespace.Bou ndColumn :
System.Web.UI.W ebForms.BoundCo lumn) which also contain a property "Key" of
type string (from an interface).

DataGridColumnC ollection cannot be inherited.

Anyone have an idea on how to do this without creating a new property (e.g.
myColumns of type myDataGridColum nCollection).

TIA.

Matt.

[Jeffrey Tan[MSFT]]

Hi Matt,

Thanks for posting in this group.
I think when initialize, you can store the key/value pairs in a hashtable,
the key is you wanted string. Then you can use string through the hashtable
to get the index of the column.

Hope this helps,

Best regards,
Jeffrey Tan
Microsoft Online Partner Support
Get Secure! - www.microsoft.com/security
This posting is provided "as is" with no warranties and confers no rights.

--------------------
| From: "Matt" <no****@hotmail .com>
| Subject: Extending a Collection indexer
| Date: Thu, 13 Nov 2003 22:17:49 -0000
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|
| Hi,
|
| I've been thinking about how to do this, but can't think of a solution.
|
| I have a class that is derived from System.Web.UI.W ebControls.Data Grid
which
| works a treat, but I'd like to extend the DataGridColumnC ollection class
| (property of DataGrid) just a fraction by allowing a string indexer. i.e.
| rather than using
|
| myDataGrid.Colu mns[7].Visible = false;
|
|
|
| I'd like to be able to do this:
|
|
|
| myDataGrid.Colu mns["Balance"].Visible = false;
|
|
|
| Background: We have a design where only certain columns are shown
depending
| on the currently logged in user's roles. Management tend to keep changing
| the layout by moving columns around, creating havoc in the code behind as
| hiding/showing columns is currently done by using the indexer as shown
| above. Moving column 7 to column 9 causes problems if you forget to
change
| the role checks for columns above 8 etc. I've introduced int constants
now
| for column names to help a bit, but still can create problems if not done
| correctly. It would be nicer to use "Key" names. All columns of
myDataGrid
| derive from their parent (eg myNamespace.Bou ndColumn :
| System.Web.UI.W ebForms.BoundCo lumn) which also contain a property "Key" of
| type string (from an interface).
|
|
|
| DataGridColumnC ollection cannot be inherited.
|
|
|
| Anyone have an idea on how to do this without creating a new property
(e.g.
| myColumns of type myDataGridColum nCollection).
|
|
|
| TIA.
|
| Matt.
|
|
|

[Matt]

Hi Jeffrey

Thanks for your response, but I don't fully understand what you imply

I could create a new Hashtable property with the string/value pairs, but his is no different really from just using int constants

What I'm trying to acheive is to be able to extend the current "Columns" property (of type DataGridCollect ion)

I've created a new property to by class myDataGrid

private myNamespace.Dat aGridColumnColl ection _dataGridColumn Collection

/// <summary
/// Gets columns by their key attribute
/// </summary
public virtual System.Web.UI.W ebControls.Data GridColumnColle ction ColumnsByKe

ge

if (_dataGridColum nCollection == null

_dataGridColumn Collection = new myNamespace.Dat aGridColumnColl ection()
_dataGridColumn Collection.Colu mnSource = Columns
return _dataGridColumn Collection

And the (proxy) collection class

/// <summary
/// myNamespace.Dat aGridColumnColl ection
/// </summary
public class DataGridColumnC ollection //: IEnumerable - removed to display less code

private System.Web.UI.W ebControls.Data GridColumnColle ction _columnSource

public DataGridColumnC ollection(

protected internal System.Web.UI.W ebControls.Data GridColumnColle ction ColumnSourc

get {return _columnSource;
set {_columnSource = value;
public System.Web.UI.W ebControls.Data GridColumn this[string Key

ge

for (int i=0; i<_columnSource .Count; i++
if (((IVPGridColum n)_columnSource[i]).Key == Key
return _columnSource[i]

return null


Now I have 2 properties for my DataGrid which return the same collection: "Columns" and "ColumnsByK ey"

What I really want is to extend the orignal property "Columns" by creating a property this[string Key] for it. However I can't derive from System.Web.UI.W ebControls.Data GridColumnColle ction

Is it possible to do this

I hope this makes sense

TIA

Matt.

[Jeffrey Tan[MSFT]]

Hi,

Sorry, based on my understanding, you can do like this:
Hashtable ht=new Hashtable();
ht.Add("Balance ",7);
DataGrid1.Colum ns[(int)ht["Balance"]].Visible=false;

I think this is equivalent to DataGrid1.Colum ns[7].Visible=false;

If I still misunderstandin g you, please feel free to let me know.

Best regards,
Jeffrey Tan
Microsoft Online Partner Support
Get Secure! - www.microsoft.com/security
This posting is provided "as is" with no warranties and confers no rights.

--------------------
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<ry************ **@cpmsftngxa06 .phx.gbl>
| Subject: RE: Extending a Collection indexer
| Date: Fri, 14 Nov 2003 02:11:06 -0800
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|
| Hi Jeffrey,

Thanks for your response, but I don't fully understand what you imply.

I could create a new Hashtable property with the string/value pairs, but
his is no different really from just using int constants.

What I'm trying to acheive is to be able to extend the current "Columns"
property (of type DataGridCollect ion).

I've created a new property to by class myDataGrid:
private myNamespace.Dat aGridColumnColl ection _dataGridColumn Collection;

/// <summary>
/// Gets columns by their key attribute.
/// </summary>
public virtual System.Web.UI.W ebControls.Data GridColumnColle ction
ColumnsByKey
{
get
{
if (_dataGridColum nCollection == null)
{
_dataGridColumn Collection = new myNamespace.Dat aGridColumnColl ection();
_dataGridColumn Collection.Colu mnSource = Columns;
}

return _dataGridColumn Collection;
}
}
And the (proxy) collection class:

/// <summary>
/// myNamespace.Dat aGridColumnColl ection.
/// </summary>
public class DataGridColumnC ollection //: IEnumerable - removed to display
less code.
{
private System.Web.UI.W ebControls.Data GridColumnColle ction _columnSource;

public DataGridColumnC ollection()
{
}

protected internal System.Web.UI.W ebControls.Data GridColumnColle ction
ColumnSource
{
get {return _columnSource;}
set {_columnSource = value;}
}

public System.Web.UI.W ebControls.Data GridColumn this[string Key]
{
get
{
for (int i=0; i<_columnSource .Count; i++)
if (((IVPGridColum n)_columnSource[i]).Key == Key)
return _columnSource[i];

return null;
}
}
}
Now I have 2 properties for my DataGrid which return the same collection:
"Columns" and "ColumnsByK ey".

What I really want is to extend the orignal property "Columns" by creating
a property this[string Key] for it. However I can't derive from
System.Web.UI.W ebControls.Data GridColumnColle ction.

Is it possible to do this?

I hope this makes sense.

TIA,

Matt.
|

[Matt]

Thanks for your help.

Matt.

""Jeffrey Tan[MSFT]"" <v-*****@online.mi crosoft.com> wrote in message
news:nh******** ******@cpmsftng xa06.phx.gbl...

Hi,

Sorry, based on my understanding, you can do like this:
Hashtable ht=new Hashtable();
ht.Add("Balance ",7);
DataGrid1.Colum ns[(int)ht["Balance"]].Visible=false;

I think this is equivalent to DataGrid1.Colum ns[7].Visible=false;

If I still misunderstandin g you, please feel free to let me know.

Best regards,
Jeffrey Tan
Microsoft Online Partner Support
Get Secure! - www.microsoft.com/security
This posting is provided "as is" with no warranties and confers no rights.

--------------------
| Thread-Topic: Extending a Collection indexer
| thread-index: AcOql52oJ+toVC8 AQIKSMcrk0va2dQ ==
| X-Tomcat-NG: microsoft.publi c.dotnet.langua ges.csharp
| From: "=?Utf-8?B?TWF0dA==?=" <an*******@disc ussions.microso ft.com>
| References: <O1************ **@TK2MSFTNGP11 .phx.gbl>
<ry************ **@cpmsftngxa06 .phx.gbl>
| Subject: RE: Extending a Collection indexer
| Date: Fri, 14 Nov 2003 02:11:06 -0800
| Lines: 75
| Message-ID: <74************ *************** *******@microso ft.com>
| MIME-Version: 1.0
| Content-Type: text/plain;
| charset="Utf-8"
| Content-Transfer-Encoding: 7bit
| X-Newsreader: Microsoft CDO for Windows 2000
| Content-Class: urn:content-classes:message
| Importance: normal
| Priority: normal
| X-MimeOLE: Produced By Microsoft MimeOLE V6.00.3790.0
| Newsgroups: microsoft.publi c.dotnet.langua ges.csharp
| NNTP-Posting-Host: TK2MSFTCMTY1 10.40.1.180
| Path: cpmsftngxa06.ph x.gbl!cpmsftngx a10.phx.gbl
| Xref: cpmsftngxa06.ph x.gbl microsoft.publi c.dotnet.langua ges.csharp:1992 84 | X-Tomcat-NG: microsoft.publi c.dotnet.langua ges.csharp
|
| Hi Jeffrey,

Thanks for your response, but I don't fully understand what you imply.

I could create a new Hashtable property with the string/value pairs, but
his is no different really from just using int constants.

What I'm trying to acheive is to be able to extend the current "Columns"
property (of type DataGridCollect ion).

I've created a new property to by class myDataGrid:
private myNamespace.Dat aGridColumnColl ection _dataGridColumn Collection;

/// <summary>
/// Gets columns by their key attribute.
/// </summary>
public virtual System.Web.UI.W ebControls.Data GridColumnColle ction
ColumnsByKey
{
get
{
if (_dataGridColum nCollection == null)
{
_dataGridColumn Collection = new myNamespace.Dat aGridColumnColl ection();
_dataGridColumn Collection.Colu mnSource = Columns;
}

return _dataGridColumn Collection;
}
}
And the (proxy) collection class:

/// <summary>
/// myNamespace.Dat aGridColumnColl ection.
/// </summary>
public class DataGridColumnC ollection //: IEnumerable - removed to display
less code.
{
private System.Web.UI.W ebControls.Data GridColumnColle ction _columnSource;

public DataGridColumnC ollection()
{
}

protected internal System.Web.UI.W ebControls.Data GridColumnColle ction
ColumnSource
{
get {return _columnSource;}
set {_columnSource = value;}
}

public System.Web.UI.W ebControls.Data GridColumn this[string Key]
{
get
{
for (int i=0; i<_columnSource .Count; i++)
if (((IVPGridColum n)_columnSource[i]).Key == Key)
return _columnSource[i];

return null;
}
}
}
Now I have 2 properties for my DataGrid which return the same collection:
"Columns" and "ColumnsByK ey".

What I really want is to extend the orignal property "Columns" by creating
a property this[string Key] for it. However I can't derive from
System.Web.UI.W ebControls.Data GridColumnColle ction.

Is it possible to do this?

I hope this makes sense.

TIA,

Matt.
|