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changes-on-items-in-report-events-are-not-applied.md

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Changes on Items in Report Events Are Not Applied
Learn why the modifying of report items in report event handlers may not work after R3 2016 Telerik Reporting release.
how-to
Editing report items in report events does not take effect
changes-on-items-in-report-events-are-not-applied
kb

Environment

Product Progress® Telerik® Reporting

Description

In Telerik Reporting versions prior to R3 2016, all changes in events were accepted, even these applied on items' definitions. When items' definitions were modified in the event handlers, changes were applied on all consecutive processing elements with the expected result.

Modifying report in events prior to R3 2016:

void report_NeedDataSource(object sender, EventArgs e)
{
	this.DataSource = GetReportData();
	this.table.DataSource = GetTableData();
}

With [R3 2016]({%slug telerikreporting/upgrade/2016/r3-2016%}#api-breaking-changes), we applied an optimization change in the report rendering algorithm and now each definition item property values are read and cached once the report rendering starts.

If you are working with item definitions in events, they may remain unchanged. For more details, check the updated [Understanding Events]({%slug telerikreporting/using-reports-in-applications/program-the-report-definition/report-events/understanding-events%}) help article.

Solution

  • Modifying Report item in events after R3 2016:

    

    • 



void report_NeedDataSource(object sender, EventArgs e)
{
Telerik.Reporting.Processing.Report processingReport = (Telerik.Reporting.Processing.Report)sender;
processingReport.DataSource = GetReportData();
}



	> In the report `NeedDataSource` and `ItemDataBinding` events, the processing instances of the other report items are not created yet. Hence, it is not possible to modify other items in these Report events.

* Modifying other items in events after **R3 2016**:

	````C#
void table_NeedDataSource(object sender, EventArgs e)
	{
		Telerik.Reporting.Processing.Table processingTable = (Telerik.Reporting.Processing.Table)sender;
		processingTable.DataSource = GetTableData();
	}



In all versions of Telerik Reporting, changes in events are possible if they are applied on the processing elements, not the items' definitions (report elements accessible through this. in C# or Me. in VB.NET). The valid approaches are illustrated in [Accessing Report Items Programmatically]({%slug telerikreporting/using-reports-in-applications/program-the-report-definition/access-report-items-programmatically%}).


The recommended approach is to use the expression engine and to avoid custom code in events:


    

  1. [Conditional Formatting]({%slug telerikreporting/designing-reports/styling-reports/conditional-formatting%}) to control styles via expressions;
    2. 

  2. [Bindings]({%slug telerikreporting/designing-reports/connecting-to-data/expressions/using-expressions/bindings%}) to set properties of items via expressions;
    3. 

  3. [User functions]({%slug telerikreporting/designing-reports/connecting-to-data/expressions/extending-expressions/user-functions%}) to set properties of items, when the [built-in functions]({%slug telerikreporting/designing-reports/connecting-to-data/expressions/expressions-reference/overview%}) are not sufficient.
    4. 



The usage of the expression engine assures items will be modified at the right moment.


Notes


If you have many legacy reports and changing the code in events in all of them is not an option, you could give up on the property resolution optimization and turn it off. To do so, apply the following settings in [Telerik.Reporting configuration section]({%slug telerikreporting/using-reports-in-applications/export-and-configure/configure-the-report-engine/overview%}#telerik-reporting-configuration-section) in application configuration file:


<?xml version="1.0" encoding="utf-8" ?>
<configuration>
	<!-- section handler ok; 1 extension  -->
	<configSections>
		<section
			name="Telerik.Reporting"
			type="Telerik.Reporting.Configuration.ReportingConfigurationSection, Telerik.Reporting.Configuration, Culture=neutral, PublicKeyToken=a9d7983dfcc261be"
			allowLocation="true"
			allowDefinition="Everywhere"/>
	</configSections>
	//...
	<Telerik.Reporting>
		<processing cacheDefinitionProperties="false" />
	</Telerik.Reporting>
</configuration>


See Also


    

  • [How to use the ReportItem.DataObject property in expressions]({%slug telerikreporting/designing-reports/connecting-to-data/data-items/how-to-use-the-reportitem.dataobject-property-in-expressions%})
    • 

  • [Databind to Collection Properties]({%slug how-to-databind-to-collection-properties%})
    • 

  • [How to bind Sub Report to Main Report's Data]({%slug how-to-bind-sub-report-to-main-report-s-data%})
    • 

  • [Change Sub Report based on Main Report's Data]({%slug change-sub-report-based-on-main-report-s-data%})
    • 

  • [Changing the connection string dynamically according to runtime data]({%slug changing-the-connection-string-dynamically-according-to-runtime-data%})
    •