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Report Application Server .NET SDK Developer Guide
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Setting dynamic cascading parameters
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You can preset the parameter values of the first n levels of a cascading prompt group so that the user viewing the report only needs to select values from a subset of the parameters. There are some factors to consider when using dynamic cascading parameters to add this functionality to your application:
- Only dynamic cascading prompts that have a parameter associated with them can be programmatically set. For example, if a prompt group only has a parameter associated with its lowest level, you can only set a parameter value for that one level.
- A cascading parameter prompt group can only be partially set when viewing the report at run-time. Reports can't be saved in a state where only some of the parameters in a cascading prompt are set. Either all the cascading parameters are set and saved back to the report (as saved data), or none of the cascading parameter values are saved (user is prompted to select parameter values when viewing).
- Only valid, matching values that are set at all levels of a cascading prompt group will ensure the report displays correctly. Validity is important because no restrictions or exceptions are thrown programmatically if you set invalid values. For example, if you have a 'Country', 'Region', and 'City' set of cascading parameters, and you set the values to 'USA', 'CA' and 'Paris' respectively ('Paris' being an invalid value for this country and region), the viewer will try to display the report with those mismatching values with unpredictable results. However, if you are setting only a subset of the levels to trigger a prompt dialog box for users, and you have mismatching values, any invalid cascading values will be discarded so the prompt dialog box can be displayed correctly.
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 Note
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The ReportClientDocument object model does not currently support creating new prompt groups programmatically and saving them to the report. For more information about dynamic cascading parameters and creating prompt groups with the Crystal Reports Designer, see the Crystal Reports User's Guide.
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This example programmatically sets the first two parameters of a three-level, dynamic cascading prompt in a report. The report has three dynamic cascading parameters: 'Country', 'Region', and 'City'. These values will be pre-populated when the prompt dialog box is rendered, and they will filter the allowed values of the third level parameter, 'City', which can be entered by the user.
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Visual Basic
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Private Sub SetDynamicCascadingParameters(ByVal rcd As ISCDReportClientDocument)
rcd.DataDefController.ParameterFieldController.SetCurrentValue("", "Location - Country", "USA")
rcd.DataDefController.ParameterFieldController.SetCurrentValue("", "Location - Region", "CA")
myCrystalReportViewer.ReportSource = rcd
End Sub
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C#
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private void SetDynamicCascadingParameters(ISCDReportClientDocument rcd)
{
rcd.DataDefController.ParameterFieldController.SetCurrentValue("", "Location - Country", "USA");
rcd.DataDefController.ParameterFieldController.SetCurrentValue("", "Location - Region", "CA");
crystalReportViewer.ReportSource = rcd;
}
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This list includes the namespaces used by the sample code:
- CrystalDecisions.Enterprise
- CrystalDecisions.ReportAppServer.ClientDoc
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