[Solved] GridCalculatedColumn and EnableLinqExpressions=False cause Exception

[Constantin]

Hi,

we have encountered a problem with the GridCalculatedColumn and EnableLinqExpressions = false where we receive an Exception on every PageLoad


Minimal Test Case: 

<telerik:RadGrid ID="RadGrid1" DataSourceID="XmlDataSource1" runat="server" Width="990px"
    EnableLinqExpressions="False">
    <MasterTableView AutoGenerateColumns="False">
        <Columns>
            <telerik:GridBoundColumn runat="server" UniqueName="value1" DataField="value1" HeaderText="Value 1" />
            <telerik:GridBoundColumn runat="server" UniqueName="value1" DataField="value1" HeaderText="Value 2" />
            <telerik:GridCalculatedColumn runat="server" Expression="value1 + value2" />
        </Columns>
    </MasterTableView>
</telerik:RadGrid>
<asp:xmldatasource id="XmlDataSource1" runat="server" datafile="Source.xml" xpath="DataPoints/Point"/>

source.xml

<?xml version="1.0" encoding="utf-8" ?>
<DataPoints>
  <Point Value1="1" Value2="2"/>
</DataPoints>

This yields the Exception:

Server Error in '/Example' Application.

---

Cannot remove this column, because it is part of an expression: column = value1 + value2.

Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code. 

Exception Details: System.ArgumentException: Cannot remove this column, because it is part of an expression: column = value1 + value2.

Source Error: 

An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below.

Stack Trace: 

[ArgumentException: Cannot remove this column, because it is part of an expression: column = value1 + value2.] System.Data.DataColumnCollection.CanRemove(DataColumn column, Boolean fThrowException) +1865260 System.Data.DataColumnCollection.BaseRemove(DataColumn column) +25 System.Data.DataColumnCollection.Remove(DataColumn column) +53 Telerik.Web.UI.GridDataTableFromEnumerable.GetColumnsToUse() +6962 Telerik.Web.UI.GridDataTableFromEnumerable.FillData() +661 Telerik.Web.UI.GridResolveEnumerable.Initialize() +32 Telerik.Web.UI.GridResolveEnumerable.EnsureInitialized() +20 Telerik.Web.UI.GridEnumerableFromDataView..ctor(GridTableView owner, IEnumerable enumerable, Boolean CaseSensitive, Boolean autoGenerateColumns, GridColumnCollection presentColumns, String[] additionalField, Boolean retrieveAllFields, Boolean enableSplitHeaderText) +163 Telerik.Web.UI.GridDataSourceHelper.CreateGridEnumerable(GridTableView owner, IEnumerable enumerable, Boolean caseSensitive, Boolean autoGenerateColumns, GridColumnCollection presentColumns, String[] additionalField, Boolean retrieveAllFields, Boolean enableSplitHeaderText) +129 Telerik.Web.UI.GridDataSourceHelper.GetResolvedDataSource(GridTableView owner, Object dataSource, String dataMember, Boolean caseSensitive, Boolean autoGenerateColumns, GridColumnCollection presentColumns, String[] additionalField, Boolean retrieveAllFields, Boolean enableSplitHeaderText) +398 Telerik.Web.UI.GridTableView.get_ResolvedDataSource() +159 Telerik.Web.UI.GridTableView.CreateControlHierarchy(Boolean useDataSource) +316 Telerik.Web.UI.GridTableView.CreateChildControls(IEnumerable dataSource, Boolean useDataSource) +550 System.Web.UI.WebControls.CompositeDataBoundControl.PerformDataBinding(IEnumerable data) +57 System.Web.UI.WebControls.DataBoundControl.OnDataSourceViewSelectCallback(IEnumerable data) +114 System.Web.UI.DataSourceView.Select(DataSourceSelectArguments arguments, DataSourceViewSelectCallback callback) +31 System.Web.UI.WebControls.DataBoundControl.PerformSelect() +142 Telerik.Web.UI.GridTableView.PerformSelect() +16 System.Web.UI.WebControls.BaseDataBoundControl.DataBind() +73 Telerik.Web.UI.GridTableView.DataBind() +229 Telerik.Web.UI.RadGrid.DataBind() +80 System.Web.UI.WebControls.BaseDataBoundControl.EnsureDataBound() +82 System.Web.UI.WebControls.CompositeDataBoundControl.CreateChildControls() +72 System.Web.UI.Control.EnsureChildControls() +87 System.Web.UI.Control.PreRenderRecursiveInternal() +44 System.Web.UI.Control.PreRenderRecursiveInternal() +171 System.Web.UI.Control.PreRenderRecursiveInternal() +171 System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +842

Using Telerik Q2-2012-SP2 (2012.2.912.35)

[Kostadin]

Hello Constantin,

When you are binding through XmlDataSource, each node will become a row and each attribute represents a column. The name of the attribute is the header text of the given column. In this scenario is better to use the GridTemplateColumn instead GridCalculatedColumnd as it is hard to define the data type of the XML items.

<telerik:RadGrid ID="RadGrid2" runat="server" CellSpacing="0" DataSourceID="XmlDataSource1"
    GridLines="None" EnableLinqExpressions="true" OnItemDataBound="RadGrid2_ItemDataBound">
    <MasterTableView AutoGenerateColumns="False" DataSourceID="XmlDataSource1">
        <Columns>
            <telerik:GridBoundColumn DataField="Value1" HeaderText="Value1" SortExpression="Value1"
                UniqueName="Value1">
            </telerik:GridBoundColumn>
            <telerik:GridBoundColumn DataField="Value2" HeaderText="Value2" SortExpression="Value2"
                UniqueName="Value2">
            </telerik:GridBoundColumn>
            <telerik:GridTemplateColumn HeaderText="Total" UniqueName="Temp">
                <ItemTemplate>
                    <asp:Label ID="Label1" runat="server"></asp:Label>
                </ItemTemplate>
            </telerik:GridTemplateColumn>
        </Columns>
    </MasterTableView>
</telerik:RadGrid>
<asp:XmlDataSource ID="XmlDataSource1" runat="server" DataFile="~/source.xml"></asp:XmlDataSource>

I also attached the sample so you could take a look at it.

Greetings,
Kostadin
the Telerik team

[Constantin]

The problem exists with other DataSources type (for example ObjectDataSource) as well.
This was just a quick sample to give you a test case.

The problem with the GridTemplateColumn is that you lose sorting based on the calculated value, which is what we need the GridCalculatedColumn for to begin with.

[Kostadin]

Hello Constantin,

I was not able to reproduce the same exception with SqlDatasource. I attached a sample where you could see that filtering and sorting work properly when EnableLinqExpressions is set to false. You could check this forum where the same exception is already discussed and might prove helpful in your case.

Regards,
Kostadin
the Telerik team

[Constantin]

Hi Kostadin,

thanks for the reply. Working with example I was able to further narrow the problem down. Posting it here for others that may have a similar issue.

You must specify the DataFields you want to use in the expression, regardless of wether you want to use the Placeholder {0} notation or full DataField names in the Expression. If you fail to specify all DataFields used by your Expression you get the Exception mentioned above.

[Peter]

I don't understand this problem... I simply have a calculated column inside a child DetailsTable in a Rad Grid:

<telerik:GridCalculatedColumn DataFields="" Expression="HourlyRate * 38 * 52" UniqueName="AnnualRateCalc" HeaderText="Annual Rate (Calc)" DataFormatString="{0:c}" DataType="System.Decimal" />

How do I fix this?

[Princy]

Hi Peter,

You should set the DataFields property of the GridCalculatedColumn and use it in the Expression. Use the DataFields property to list all the fields that are used to calculate the column value. The Expression property specifies how the field values are to be combined, using parameters based on the order of the fields listed in the DataFields property:

ASPX:

<telerik:GridCalculatedColumn DataFields="HourlyRate" Expression="{0} * 38 * 52" . . . />

Thanks,
Princy

[Peter]

Yes thanks - it's been too long since I used a calculated column... I was thrown-off by the error: "Cannot remove this column, because it is part of an expression: AnnualRateCalc = HourlyRate * 38 * 52."