databinding, Binding multiple checkboxes to a single data field

by **Jeronimo Bertran** » Wed, 20 Apr 2005 14:17:59 GMT

I have a form that uses databinding to update a database table. One of the
fields in the table corresponds to multiple checkbox controls in the form
(Flags Attributes). How can I perform the databinding in this case?

Thanks,

Jeronimo Bertran

by **v-jetan** » Wed, 20 Apr 2005 17:19:24 GMT

Hi Jeronimo,

Thanks for your post!!

For checkboxes, we should use simple databinding to bind to the DataTable.
To do simple databinding, we can use CheckBox.DataBindings property, with
this property, we can associate multi-checkboxes' Checked property with the
bool column in the underlying datatable. Sample code lists below:
private void Form1_Load(object sender, System.EventArgs e)
{
this.checkBox1.DataBindings.Add("Checked", dt, "boolcolumn");
this.checkBox2.DataBindings.Add("Checked", dt, "boolcolumn");
}
Once these checkboxes have the same datasource, its checked state will keep
synchronized each other.(That is if we unchecked one checkbox, then other
checkboxes will become unchecked either)

Hope this helps.
===============================================
Thank you for your patience and cooperation. If you have any questions or
concerns, please feel free to post it in the group. I am standing by to be
of assistance.

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.

by **Jeronimo Bertran** » Thu, 21 Apr 2005 01:52:15 GMT

Hi Jeffrey,

I noticed that I didn't express the problem very clearly... the problem I
have is that the underlying field does not represent a single checkbox but
it represents multiple distinct checkboxes. It is in fact a Flags integer
value that is stored on the database... here is an example:

[FlagsAttribute]
public enum MyFlags
{
none = 0x00,
flag1 = 0x01,
flag2 = 0x02
};

public MyFlags flags;

flags = (MyFlags) Row.Flags;

checkBox1.Checked = ((flags & flag1) != MyFlags.none);
checkBox2.Checked = ((flags & flag2) != MyFlags.none);

Thanks again,

Jeronimo

by **Jeronimo Bertran** » Thu, 21 Apr 2005 02:53:07 GMT

I figured out how to do part of the work:

I created a property for each flag in my form:

public bool Flag1
{
get { return (flags & Flags.flag1) != Flags.none;}
set
{
if (value)
flags |= Flags.flag1;
else
flags &= ~Flags.flag1;
}
}

I then added the databinding:

this.checkBox1.DataBindings.Add("Checked", this, "Flag1");

This will keep the variable flag in synch with the controls.... however I
am still missing the databinding from the flags variable to the dataset. I
should mention that I am relying on the RowChanging event to confirm with
the user if changes should be saved and simply updating the row with the
new flags value will not generate this event when I end the current edit.

Thanks again.

by **a2Fib3JrYQ** » Thu, 21 Apr 2005 05:43:03 GMT

I use custom Format and Parse handlers to convert between the CheckBox bool
value and whatever is in the database. In the example below, the handlers
convert true/false to "Y"/"N". You can write your own handlers to mask the
checkbox values to the corresponding part of the database field. Sounds like
you'd need a different pair of handlers for each checkbox, all bound to the
same field. See help for Binding.Format and .Parse. I'm wondering if you
might get exceptions about multiple bindings to the same field. Hope this
helps!

-----------------------------------------------------------
// bind the checkbox value to the bool column
Binding b = new Binding(@"Checked", dsService.dataService,

dsService.dataService.IsUserRouteStrColumn.ColumnName);
// the binding needs a format handler to convert Y/N to bool, and a parse
handler to convert back
b.Format += new ConvertEventHandler(ConvertYesNoToBoolHandler);
b.Parse += new ConvertEventHandler(ConvertBoolToYesNoHandler);
chkRouteStr.DataBindings.Add(b);

by **v-jetan** » Thu, 21 Apr 2005 16:04:37 GMT

Hi Jeronimo,

Yes, with your further good explaination I think I understand your scenario
and problem.

I think kaborka has pointed you the correct direction. For such simple
databinding, we can leverage Binding object's Parse and Format event to
hook into the binding process. In Binding.Format event, we can dynamically
get the underlying field's value through ConvertEventArgs.Value proerty and
apply your program logic to parse this value into Bool type. Also, once the
user changed checkbox's checked state at UI side, Binding.Parse event will
fire, then we can apply the reverse logic in this event to parse the
checked state into certain MyFlags type.

I have writen a little sample code snippet, which demostrate how to
implement Format event:

private void button1_Click(object sender, System.EventArgs e)
{
MyClass []obj=new MyClass[5];
for(int i=0;i<5;i++)
{
obj[i]=new MyClass();
obj[i].Flags=(MyFlags)(i%3);
}
Binding b1=new Binding("Checked", obj, "Flags");
b1.Format+=new ConvertEventHandler(b1_Format);

Binding b2=new Binding("Checked", obj, "Flags");
b2.Format+=new ConvertEventHandler(b2_Format);

this.checkBox1.DataBindings.Add(b1);
this.checkBox2.DataBindings.Add(b2);
}

private void b1_Format(object sender, ConvertEventArgs e)
{
if(e.DesiredType==typeof(bool))
{
e.Value=((((MyFlags)e.Value)&MyFlags.flag1) != MyFlags.none);
}
}

private void b2_Format(object sender, ConvertEventArgs e)
{
if(e.DesiredType==typeof(bool))
{
e.Value=((((MyFlags)e.Value)&MyFlags.flag2) != MyFlags.none);
}
}

private void button2_Click(object sender, System.EventArgs e)
{
this.checkBox1.DataBindings["Checked"].BindingManagerBase.Position=
(this.checkBox1.DataBindings["Checked"].BindingManagerBase.Position+1)%5;
}
The code in button2_Click just changes binding object position, then the UI
side checkbox state should change correspondingly.
It works well on my side. Thanks
=================================================================
Thank you for your patience and cooperation. If you have any questions or
concerns, please feel free to post it in the group. I am standing by to be
of assistance.

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.

by **Jeronimo Bertran** » Fri, 22 Apr 2005 04:30:19 GMT

Thanks to both of you...

I will test it.

Jeronimo

by **v-jetan** » Fri, 22 Apr 2005 10:14:25 GMT

Ok, please feel free to feedback your test result here. Thanks

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.

databinding, Binding multiple checkboxes to a single data field

databinding >> Binding multiple checkboxes to a single data field

databinding >> RE: Binding multiple checkboxes to a single data field

databinding >> RE: Binding multiple checkboxes to a single data field

databinding >> RE: Binding multiple checkboxes to a single data field

databinding >> RE: Binding multiple checkboxes to a single data field

databinding >> RE: Binding multiple checkboxes to a single data field

databinding >> RE: Binding multiple checkboxes to a single data field

databinding >> RE: Binding multiple checkboxes to a single data field