Скачать или смотреть How to Show Selected Value in a DropDownList Using ViewBag in C#

Discover how to effectively display the selected value in a DropDownList with Razor in C# . Learn to utilize ViewBag for dynamic data binding in ASP.NET MVC applications.
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This video is based on the question https://stackoverflow.com/q/71511745/ asked by the user 'Rahul Sharma' ( https://stackoverflow.com/u/1807452/ ) and on the answer https://stackoverflow.com/a/71513062/ provided by the user 'Serge' ( https://stackoverflow.com/u/11392290/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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How to Show Selected Value in a DropDownList Using ViewBag in C#

In web development, especially within the context of ASP.NET MVC, you might encounter a situation where you need to show a pre-selected value in a DropDownList. The ideal way to achieve this is by using the ViewBag to pass dynamic data from your controller to your view. In this guide, we will explore a practical scenario to demonstrate how to bind a DropDownList to a selected value using ViewBag. This will guide you in efficiently utilizing these tools in your ASP.NET MVC applications.

The Scenario

Consider you're developing a form that requires a user to select an option from a dropdown. You will use two ViewBag properties:

To hold the list of items for the dropdown.

To store the currently selected value.

Here’s a sample code snippet that represents this scenario:

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In your Razor view, you might attempt to generate the dropdown like this:

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

However, the challenge arises when you want to have the DropDownList display the selected value by default when the component is rendered.

The Solution

To display the selected value correctly, you need to make a few adjustments. Relying solely on ViewBag might not work as intended for setting the selected item. Instead, you can utilize a SelectList that allows you to explicitly set the selected value while generating the dropdown.

Step 1: Create the SelectList with Selected Value

Use the SelectList constructor to specify which item should be selected by default. Here’s how you would modify your Razor view code:

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

Step 2: Generate the DropDownList

Once you've created the SelectList, you can generate the dropdown in a straightforward manner:

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

Final Razor View Code Example

Here’s how your final Razor view might look:

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

Conclusion

With these adjustments, your DropDownList will successfully display the selected value based on the current context. Utilizing SelectList provides a robust way to bind dropdown options while maintaining clarity in your code.

This approach not only simplifies your dropdown handling but also enhances the user experience by showing pre-selected options neatly. Now you're ready to implement this in your own ASP.NET MVC applications effectively!