DxReportDesignerCallbacks.PreviewParametersInitialized Property

Specifies the JavaScript function that handles the PreviewParametersInitialized client-side event and allows you to get the client-side parameter values when they are initialized in the Designer Preview and modify them.

Namespace: DevExpress.Blazor.Reporting

Assembly: DevExpress.Blazor.Reporting.v25.1.JSBasedControls.Common.dll

NuGet Package: DevExpress.Blazor.Reporting.JSBasedControls.Common

Declaration

C#

[Parameter]
public string PreviewParametersInitialized { get; set; }

VB.NET

<Parameter>
Public Property PreviewParametersInitialized As String

Property Value

Type	Description
String	The name of a JavaScript function or entire JavaScript function code that runs when the PreviewParametersInitialized event occurs.

Remarks

The ParametersInitialized event allows you to get client-side parameter values when they are initialized, subscribe to their changes, and fill parameter editors with custom parameter values.

The handler function receives two arguments - the first argument is the client-side DocumentViewer object (Preview if the ReportDesigner’s event is handled); the second argument is the object with the following properties and methods:

ActualParametersInfo

An array of objects with information about parameters. Each object contains the following properties and methods:

• parameterDescriptor

  An object with the IParameterDescriptor interface. It contains a parameter description and indicates whether a parameter has lookup values.

• lookupValues

  Returns a ko.ObservableArray<IDisplayedValue> array of the parameter lookup values {value, displayValue}.

• value

  Returns the ko.Observable | ko.Computed parameter value. Subscribe to this value to handle user changes to the parameter value in the editor.

Submit

A method that initiates document generation.

ShouldRequestParameters

Returns true if the report’s RequestParameters property is true and the report has at least one visible parameter. Otherwise, the property returns `false.

Example: Initialize an Invisible Parameter

Use the ParametersInitialized event to set values of report parameters that are not displayed in the Preview Parameters panel.

The following code snippet sets the parameter value after the Viewer loads the report, but before the Viewer creates and displays the document. This code calls the Submit method to generate the document after the specified parameter value is applied to the report.

function onParametersInitialized(s, e) {
    var p1 = e.ActualParametersInfo
        .filter(x => x.parameterDescriptor.name == "parameter1")[0];
    p1.value = 100;
    p1 && e.Submit();
}

In Blazor Server applications, set DxDocumentViewer.AutoStartBuild to false to disable automatic report generation and avoid generating a report twice.

Example: Cascading Parameters

The following code snippet filters lookup values of the Person2 parameter based on the value selected for the Person1 parameter:

function ParametersInitialized(sender, args) {
    var parameter1 = args.ActualParametersInfo.filter(
        x => x.parameterDescriptor.name == 'Person1')[0];
    var parameter2 = args.ActualParametersInfo.filter(
        x => x.parameterDescriptor.name == 'Person2')[0];
    var preValue = null;
    parameter1.events.on('propertyChanged', (args) => {
        if(args.propertyName === 'value') {
            const newVal = args.newValue;
            var lookUps = parameter2.lookUpValues.filter(
                x => x.value != newVal);
            preValue && lookUps.push(preValue);
            preValue = parameter2.lookUpValues.filter(
                x => x.value == newVal)[0];
            parameter2.lookUpValues = lookUps;
        }
    });
    parameter1 && parameter2 && args.Submit();
}

In Blazor Server applications, set DxDocumentViewer.AutoStartBuild to false to disable automatic report generation and avoid generating a report twice.