How to Define a Global Variable in _ViewStart.cshtml for ASP.NET Core 3.1

Описание: Learn how to define a `global variable` in _ViewStart.cshtml so that all views in your ASP.NET Core 3.1 application can access it easily, minimizing code repetition.
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This video is based on the question https://stackoverflow.com/q/63390249/ asked by the user 'Aleks Vujic' ( https://stackoverflow.com/u/19397290/ ) and on the answer https://stackoverflow.com/a/63390386/ provided by the user 'Catalin' ( https://stackoverflow.com/u/1157952/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Defining a Global Variable in _ViewStart.cshtml for ASP.NET Core 3.1

In the world of web development, maintaining clean, reusable, and efficient code is crucial. One common challenge developers face is avoiding repetitive code, especially when it comes to variables that are needed across multiple views. If you are working with ASP.NET Core 3.1, you might find yourself needing to define a global variable (for example, the current user's email) that can be accessed from all views.

The Problem

Imagine you have views in your ASP.NET Core application that need to display the current user's email address. Typically, you might have to write the same code in each view to retrieve this email from claims, which is not only repetitive but can also make future updates cumbersome.

Here’s a snippet of the repetitive code you might currently use:

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This kind of duplication can be avoided by defining the variable in a central place, such as in the _ViewStart.cshtml file, where layouts and shared resources for all views are defined.

The Solution

To effectively define a global variable in _ViewStart.cshtml that can be accessed throughout all your views, you can utilize dependency injection in combination with the _ViewImports.cshtml file. Here’s a step-by-step approach:

Step 1: Define the Variable in _ViewImports.cshtml

Open your _ViewImports.cshtml file and add the following code to define and inject the user's email:

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In this code snippet:

We declare a string variable UserEmail that can be assigned the email address.

The @ inject directive allows the variable to be available in all views that render within the Razor page context.

Step 2: Accessing the Variable in Your Views

With the variable now injected, you can access it easily in any view file, including Index.cshtml. Here’s how you can use it:

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This allows you to display the user's email without having to repeat the same claim-fetching code in every view. The variable UserEmail is now globally accessible.

Conclusion

Implementing global variables in your ASP.NET Core 3.1 application can significantly reduce code duplication and improve maintainability. By defining your global email variable in _ViewImports.cshtml, and then injecting it into your views, you streamline your code while keeping it tidy and more professional.

This approach not only saves you time but also enhances the overall architecture of your application. Keep practicing these techniques to build better applications with fewer headaches!