Solving the null Selection Issue in ASP.NET Core Razor Forms

Discover how to ensure that selected items in ASP.NET Core Razor forms are correctly passed on post, with simple solutions and explanations.
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Solving the null Selection Issue in ASP.NET Core Razor Forms

If you're diving into ASP.NET Core Razor for the first time, you might run into certain challenges while implementing forms. One such issue involves getting bound properties to correctly register the selected values from dropdowns. If you've attempted to bind a dropdown selection to a property on post, only to find that the resultant value is null, you are not alone! Let's explore the problem and its immediate solution.

The Problem: Selected Value Not Being Passed

Imagine this scenario: You have a Razor page that includes a dropdown list, and you are trying to capture the user’s selection in a bound property. Despite your best efforts, the property remains null when the form is submitted. Here’s the Razor page code causing the issue:

[[See Video to Reveal this Text or Code Snippet]]

The associated code-behind looks something like this:

[[See Video to Reveal this Text or Code Snippet]]

In summary, when you try to submit the form, the dropdown's selection isn't being captured by the selectedReport property.

The Solution: Leveraging onchange Event

After some digging and testing, the answer is straightforward! You simply need to enhance your <select> element by adding an onchange event. This event will automatically submit the form whenever a selection is made. Here’s the updated code snippet:

[[See Video to Reveal this Text or Code Snippet]]

How It Works

Correct binding: With this enhancement, the selected value is now successfully bound to the selectedReport property upon form post, allowing you to handle the value in your OnPostAsync method.

Conclusion

Developing with ASP.NET Core Razor can present challenges, especially when it comes to form handling. However, adding a simple onchange event to your dropdown can resolve the issue of null values being passed in post requests. By ensuring proper binding and automatic submission, you can enhance user experience and streamline data capture in your applications.

Now that you have this solution at your disposal, you can confidently implement dropdown selections in your ASP.NET Core Razor forms without the frustration of encountering null values. Happy coding!