As virtually every product with 10+ years of development, Telerik Reporting has a certain amount of legacy code that was considered immutable at the time of writing. During the refactoring of our codebase to make it compatible with .NET Standard, we introduced a few types from System.Windows.Forms namespace to substitute the ones missing in the current version of the framework. Such types are System.Windows.Forms.CheckState and System.Windows.Forms.ControlPaint. Some of these types are introduced in recent release of .NET Core 3 for Windows Forms and therefore a conflict occurs between the types in our assemblies and the ones declared in .NET Core. The error is thrown in compile-time and it is similar to the one shown below:

The type 'CheckState' exists in both 'System.Windows.Forms, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089' and 'Telerik.Reporting, Version=13.2.19.918, Culture=neutral, PublicKeyToken=a9d7983dfcc261be'

In a future release of our product this collision will be avoided by using a dedicated enumeration for the duplicated types. A possible workaround would be to add an extern alias to the assembly reference of Telerik.Reporting. In this case all the references to Telerik.Reporting have to be edited to use the new alias, but the code that refers to the actual types from System.Windows.Forms will remain unchanged.

Here is how the Telerik.Reporting reference would look like in the application .csproj file:

  <ItemGroup>
    <Reference Include="Telerik.Reporting">
      <HintPath>..\..\..\Bin\netstandard2.0\Telerik.Reporting.dll</HintPath>
      <Aliases>telerikReporting</Aliases>
      </Reference>
  </ItemGroup>

Using the alias means that all the types in Telerik.Reporting namespace must be accessed with this alias. Unfortunately this also applies to C#/VB report definitions - their types must also be prepended with the alias, which could require significant effort. Here is a sample code file that initializes the WinForms Report Viewer and examines the CheckState of a CheckBox control in the form:

extern alias telerikReporting;

using System;
using System.Windows.Forms;

namespace WindowsFormsCoreDemo
{
    public partial class MainForm : Form
    {
        public MainForm()
        {
            InitializeComponent();
            this.Load += this.Form1_Load;
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            this.reportViewer.ReportSource = new telerikReporting::Telerik.Reporting.UriReportSource()
            {
                Uri = "SampleReport.trdp"
            };

            this.reportViewer.RefreshReport();
        }

        private void CheckBox_CheckedChanged(object sender, System.EventArgs e)
        {
            if (this.checkBox.CheckState == CheckState.Checked)
            {
                this.reportViewer.RefreshReport();
            }
        }
    }
}

When merging the ReportViewer's WPF theme dictionaries from the DLL in App.xaml, the VS2019 Designer fails due to a problem with a ZoomComboBoxStyle definition.

This causes all Telerik UI for WPF control's styles fail to load in the Visual Studio designer.

WORKAROUND

Instead of App.xaml, merge the ReportViewer's theme dictionary closer to the control.

For example in the ReportViewer's direct parent:

Hello Telerik team!

In the attachment, there are two PDFs, generated by the same template (also in attachment): one built under Windows, another one - under Linux (Docker). See red boxes as defects on the screenshot:

Text wrap issues

Dockerfile fragment:

# MS TrueTypeFonts install
RUN wget http://ftp.de.debian.org/debian/pool/contrib/m/msttcorefonts/ttf-mscorefonts-installer_3.6_all.deb -P ~/Downloads
RUN apt install -y ~/Downloads/ttf-mscorefonts-installer_3.6_all.deb

RUN apt-get install -y libc6-dev
RUN apt-get install -y libgdiplus
RUN apt-get install -y libx11-dev
RUN rm -rf /var/lib/apt/lists/*

Please help us to resolve these issues in Linux.

When you try to send the report through the SendMailMessage functionality but an exception is thrown, the report will disappear. If you click on Refresh and try again with fake data, the exception will be thrown but the report will remain. If you prefer to refresh it automatically, you can use the error event:

var viewer = $("#reportViewer1")
.telerik_ReportViewer({
    serviceUrl: "api/reports/",
    reportSource: {
        report: "Report Catalog.trdp",
    },
    error: function (e, args) {
        console.log("This event handler will be called after a page of the report is ready.");
        console.log("The error message is: " + args);
        viewer.refreshReport();
    },
    viewMode: telerikReportViewer.ViewModes.INTERACTIVE,
    scaleMode: telerikReportViewer.ScaleModes.SPECIFIC,
    scale: 1.0,
    enableAccessibility: false,
    sendEmail: { enabled: true }
}).data("telerik_ReportViewer");

running your https://demos.telerik.com/reporting in Chrome 77.0.3865.75, when trying to print the following error is returned:

Refused to execute script from 'https://p.adsymptotic.com/d/px/?_pid=16218&_psign=0aa5badf92527f7732e22463d6fa4dbc&coopa=0&gdpr=0&gdpr_consent=&_puuid=1ddd0495-ceb5-4cd4-b879-03f7c6be269b' because its MIME type ('image/gif') is not executable.

and nothing happens.

wasn't this fixed in your latest update?

is there a workable solution for this issue?

StackTrace of the error:

 System.NullReferenceException: Object reference not set to an instance of an object.
   at System.Collections.Generic.Dictionary`2.TryInsert(TKey key, TValue value, InsertionBehavior behavior)
   at Telerik.Reporting.Interfaces.LocalizationContext.GetString(String resx, String key)
   at Telerik.Reporting.SRDescriptionAttribute.get_Description()
   at Telerik.Reporting.Expressions.EnumContextManager.GetItem(Type enumType)
   at Telerik.Reporting.Processing.ReportExpressionContext.RegisterAllReportingEnums()
   at Telerik.Reporting.Processing.ReportExpressionContext..ctor(Type reportType, AssemblyRefManager assemblyRefManager)   at Telerik.Reporting.Processing.ReportParametersManager`1.CreateExpressionContext(Report report, IList`1 runtimeParameters, AssemblyRefManager references)
   at Telerik.Reporting.Processing.ReportParametersManager`1..ctor(Report definitionReport, IEnumerable`1 definitionParameters, IDictionary`2 reportSourceParameters, IDataProviderContext dataProviderContext, AssemblyRefManager references)
   at Telerik.Reporting.Processing.DocumentParametersManager`1.CreateManager(Report definition, IDataProviderContext dataProviderContext, IParameterValueParser parameterValueParser, IDictionary`2 rsParameters, AssemblyRefManager references)   at Telerik.Reporting.Processing.DocumentParametersManager`1.CreateManagers(IProcessingContext context, IParameterValueParser parameterValueParser)
   at Telerik.Reporting.Processing.DocumentParametersManager`1..ctor(ResolvedReportDocument resolvedReports, IProcessingContext processingContext, IParameterValueParser parameterValueParser)
   at Telerik.Reporting.Processing.ReportProcessor.ProcessReportSource(ReportSource reportSource, IRenderingContext context)
   --- End of inner exception stack trace ---
   at Telerik.Reporting.Processing.ReportProcessor.ProcessReportSource(ReportSource reportSource, IRenderingContext context)
   at Telerik.Reporting.Processing.ReportProcessor.ProcessReportSource(ReportSource reportSource, Hashtable deviceInfo, IRenderingContext context)
   at Telerik.Reporting.Processing.ReportProcessor.ProcessAndRender(String format, ReportSource reportSource, Hashtable deviceInfo, IRenderingContext renderingContext, CreateStream createStreamCallback)
   at Telerik.Reporting.Processing.ReportProcessor.ProcessAndRenderStateless(String format, ReportSource reportSource, Hashtable deviceInfo, IRenderingContext renderingContext, CreateStream createStreamCallback)
   at Telerik.Reporting.Processing.ReportProcessor.RenderReport(String format, ReportSource reportSource, Hashtable deviceInfo, CreateStream createStreamCallback, String& documentName)

When the user confirms changing the chart type through the "Change Chart Type" dialog window, the graph designer does not get refreshed and still shows the old chart type.

Underneath the graph item is actually changed and if the report is previewed, the new graph layout will be displayed. The current workaround is to refresh the graph designer by changing one of its properties that cause full item refresh - Culture, Graph title, NoDataMessage, etc.

The print functionality cannot be used in Google Chrome 77.0.3865.75 (lastest update).  The following error is displayed in the console of the browser: Resource interpreted as Document but transferred with MIME type application/pdf.

As an alternative, you can use other web browsers for printing.