Rider ignores Use64BitIISExpress
Answered
I am currently evaluating Rider and found a small issue. We have a ASP.net application with some 64bit dependencies. To ensure the application works during development, we have enabled the 64bit IISExpress via the Use64BitIISExpress option in the csproj. Unfortunately Rider ignores this setting and launches the 32bit IISExpress which leads to a BadImageFormatException.
Is this a known bug that will be fixed? Is there another setting that tells Rider to use the 64bit version of IISExpress? I couldn't find anything in YouTrack and also the latest Rider 2018.3 EAP6 suffers from this issue.
Kind Regards
Daniel
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Hi Daniel,
No, it is not known. I've created an issue in Rider tracker: https://youtrack.jetbrains.com/issue/RIDER-22441. Thanks for drawing our attention to it.
Workaround:
Set the path to x64 IIS Express executable and change the working directory accordingly in your run configuration:
Do you not realize that IIS 32 bit cannot be installed under Win10 64 bit ?
I've set the path to x64 IIS, but Rider still says it is not installed and wants to run the 32 bit version.
The changes I made are reset to the defaults every time I open Rider.
????
Brian Stensrud, hello. Please take into account that this is a thread about IIS Express, not IIS, and IIS Express could be installed on modern Windows in both 32-bit and 64-bit editions; I believe it even installs both versions by default. I have them both installed right now on my machine.
Could you please clarify what problems do you have with setting up IIS (Express) in Rider? What software do you have installed and which Rider settings did you change?
Note that VS2022 by default consider an empty tag
<Use64BitIISExpress />, corresponding to Default, as 64bit, while Rider 2025.3.0.3 consider it as 32bit.You need to explicitly set
<Use64BitIISExpress>true</Use64BitIISExpress>for it to work properly.