Hi Murat Şeşen,
The 404 error may be caused by issues with routing or the build process. Please ensure the @page "/todo" directive is correctly placed in your Todo.razor file and that the file is located in the Components/Pages folder. Try rebuilding the project and clearing your browser cache. If the issue persists, double-check the NavMenu link and the folder structure for any typos. I tested it on my end, and everything appears to be working correctly.
I have attached a screenshot for your reference:
Please feel free to contact us if you have any additional questions.
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