Viewer.razor

@page "/viewer"

@using DevExpress.Blazor.Reporting
@using DevExpress.XtraReports;
@using BlazorApp.Reports;

<link href="_content/DevExpress.Blazor.Themes/blazing-berry.bs5.css" rel="stylesheet" />
<link rel="stylesheet" href="_content/DevExpress.Blazor.Reporting.Viewer/css/dx-blazor-reporting-components.bs5.css">

<input @bind="paramValue" />

<button @onclick="SubmitParameter">Submit</button>

<DxReportViewer @ref="reportViewer" Report="@Report"></DxReportViewer>

@code {
    DxReportViewer reportViewer;
    string paramName = "strParam";
    string paramValue = "0";
    IReport Report;

    protected override void OnAfterRender(bool firstRender)
    {
        if (firstRender){
            var report = new XtraReport1();
            report.Parameters[paramName].Visible = false;
            Report = report;
        }

        base.OnAfterRender(firstRender);
    }

    void SubmitParameter(){
        var report = new XtraReport1();
        report.Parameters[paramName].Value = paramValue;
        report.Parameters[paramName].Visible = false;
        report.CreateDocument();
        reportViewer.TabPanelModel.Tabs[0].Visible = false;
        Report = report;
    }

}