Fixing "Could not load file or assembly Microsoft.mshtml" Error

Environment

Product

Progress® Telerik® Reporting

Description

I encounter the Could not load file or assembly Microsoft.mshtml error when working with Telerik Report Designer. This happens consistently while updating or designing reports, particularly when adding a subreport and using an HTMLTextBox for a different SQL query. The error forces the system to shut down, requiring a restart.

Solution

To resolve the "Could not load file or assembly Microsoft.mshtml" error, follow these steps:

Step 1: Copy the Assembly to the Designer Folder

1. Locate the microsoft.mshtml.dll assembly file on your system.

2. Copy the file to the Telerik Report Designer folder.

   

3. Open the report file (for example, SampleReport.trdp) and select the HTMLTextBox to check if the error is resolved.

Step 2: Add Assembly Reference to the Configuration Files

1. Open the Telerik.ReportDesigner.exe.config or Telerik.ReportDesigner.x86.exe.config file.

2. Add the following assembly reference. Ensure the <Telerik.Reporting> section is properly registered:

   <configuration>
       <configSections>
           <section name="Telerik.Reporting" type="Telerik.Reporting.Configuration.ReportingConfigurationSection, Telerik.Reporting"
                   allowLocation="true" allowDefinition="Everywhere"/>
       </configSections>
       // ...
       <Telerik.Reporting>
           <AssemblyReferences>
               <add name="Microsoft.mshtml" version="7.0.3300.0" />
           </AssemblyReferences>
       </Telerik.Reporting>
       // ...
   

3. Save the changes and relaunch Telerik Report Designer.

Step 3: Install Microsoft.mshtml in the Global Assembly Cache (GAC)

1. Open the Developer Command Prompt for Visual Studio.

   

2. Run the command gacutil /l microsoft.mshtml to check if the assembly exists in the GAC. It should display Number of items = 0 if missing.

3. Navigate to the directory containing the microsoft.mshtml.dll file.
4. Execute the following command to install the assembly: gacutil /i microsoft.mshtml.dll.
5. Verify installation with gacutil /l microsoft.mshtml.

See Also

*Global Assembly Cache (GAC) *Install an assembly into the global assembly cache