Cannot Add a blank Row to databound datagrid with Checkbox control


I think I am posting this question again but I'm quite frustrated as I haven't found any way around.

I have a databound datagrid in which New/Blank rows are added to this datagrid on a button click event. This button is outside the datagrid and not in the footer. The datagrid populates well and I can do the edit/update to the already created records. I recently had to add a new checkbox field to my data table. This chekcbox field is to be included in this datagrid. The chkbox works fine for previously created records but as soon as I hit the 'Add New Row' button I get the following error :

<i>Exception Details: System.InvalidCastException: Conversion from type 'DBNull' to type 'Boolean' is not valid.

Source Error:
Line 1176:<asp:templatecolumn headertext="Current Driver?">
Line 1177:<itemTemplate>
Line 1178:<asp:checkbox id="cbcurrentdriver" runat="server" autopostback="true" enabled ="false" checked='<%# DataBinder.Eval(Container.DataItem,"currentdriver")  %>' /></itemTemplate></i>

My code for adding a new/blank row (on button click event) is as below:
Dim ds as DataSet = DataGrid.datasource
Dim blank as DataRow = ds.tables(0).NewRow()
ds.tables(0).Rows.insertAt(blank, ds.tables(0).Rows.Count)
DataGrid.EditItemIndex = ds.tables(0).Rows.Count-1

and my checkbox template column is as below:

<i><asp:templatecolumn headertext="Current Driver?">
<asp:checkbox id="cbcurrentdriver" runat="server" autopostback="true" enabled ="false" checked='<%# DataBinder.Eval(Container.DataItem,"currentdriver")  %>' /></itemTemplate>
<headerstyle width="8%" />

I really am clueless on this one. everything seems fine. Nulls are allowed on this field in my datatable.Please help!


...we live more than once!
2/27/2007 4:51:35 AM 72751 articles. 3 followers. Follow

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Dear friend:

Make sure that there is no NULL value in the currentdriver field.

Or you can add a helper function to check whether the field contains a null field and return a default value.

checked='<%#SomeFunction( DataBinder.Eval(Container.DataItem,"currentdriver") ) %>'


I hope the above information will be helpful. If you have any issues or concerns, please let me know. It's my pleasure to be of assistance


Best Regards,
Rex Lin
Microsoft Online Community Support

If there is any question or the issue is not resolved, please feel free to mark the thread as not resolved
2/27/2007 8:03:11 AM

Hi Rex,

Thankyou for your time to go through my post.

Well I added the following in my Itemtemplate:



<asp:checkbox id="cbcurrentdriver" runat="server" autopostback="true" checked='<%# Iif(DataBinder.Eval(Container.DataItem,"currentdriver")= System.DBNull, false, DataBinder.Eval(Container.DataItem,"currentdriver")) %>'

enabled="false" />


but I get this error: BC30691: 'DBNull' is a type in 'System' and cannot be used as an expression.

I also tried '==' instead of '=' but with that I get the error  : BC30201: Expression expected.
I have also tried using 'Ctype','Convert.boolean' everything but it just does not create a blank row for me. It was working absolutely fine until I added the checkbox Template column.

Any other ideas on how I can make it work?



...we live more than once!
2/27/2007 11:24:08 PM

Dear, friend:

This works for me. You can have a look at this snippet:

public static object ValueOrNull(object value){
    return (object == DBNull.Value? null, value);

<asp:checkbox id="cbcurrentdriver" runat="server" autopostback="true" checked='<%# Convert.ToBoolean(ValueOrNull(DataBinder.Eval(Container.DataItem,"currentdriver"))%>'

I hope the above information will be helpful. If you have any issues or concerns, please let me know. It's my pleasure to be of assistance

Best Regards,
Rex Lin
Microsoft Online Community Support

If there is any question or the issue is not resolved, please feel free to mark the thread as not resolved
3/1/2007 3:37:13 AM

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