Скачать или смотреть How to Get Cell Value from GridView in C# ASP.NET

Learn how to effectively extract a cell value from a GridView in ASP.NET using C# . This guide provides a step-by-step guide and code examples for better understanding.
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This video is based on the question https://stackoverflow.com/q/66902576/ asked by the user 'Prathamesh Papinwar' ( https://stackoverflow.com/u/15457500/ ) and on the answer https://stackoverflow.com/a/66903387/ provided by the user 'erdi yılmaz' ( https://stackoverflow.com/u/6398981/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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How to Get Cell Value from GridView in C# ASP.NET

When working with ASP.NET, using a GridView to display data is quite common. However, extracting specific cell values, especially upon user interaction, can sometimes lead to confusing errors, like the "Object reference not set to an instance of an object." This post will walk you through how to correctly retrieve a cell value from a GridView, ensuring you avoid common pitfalls.

Understanding GridView in ASP.NET

The GridView control is excellent for displaying data in a tabular format and enables complex data operations such as sorting, paging, and selection. When a user clicks on a row in the GridView, you may need to retrieve information from that specific row for further processing. For example, let's consider an application that deals with COVID-19 self-declarations.

Common Scenario

Imagine you have a GridView displaying details related to employees and a user selects a row to download an attachment. Here’s what you may encounter:

Error: "Object reference not set to an instance of an object"

Reason: This often happens when trying to access a grid cell that is set as invisible in the GridView configuration.

Solution Overview: Accessing GridView Cell Values

Let's break down the solution into manageable steps:

Step 1: Verify Visibility of Cells

Check the Visibility: If you are trying to access a cell that has its visibility set to false, you won't be able to get its value, which leads to the mentioned error.

Update Your GridView: Remove the Visible="false" property for any fields you need to access in your code-behind.

For example, if one of your asp:BoundField definitions looks like this:

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

Change it to:

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

Step 2: Create a CSS Class for Styling

Instead of using the Visible property, you can implement a CSS class to hide the columns visually but still have them available in your code.

Define a CSS Class:

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

Apply the CSS Class: Add this class to your ItemStyle-CssClass and HeaderStyle-CssClass attributes.

For example:

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

Step 3: Accessing the Cell Value

Now let’s retrieve the cell value when a user interacts with the GridView:

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

Conclusion

Now you have a clear and comprehensive method to retrieve cell values from a GridView in ASP.NET. Ensure your necessary fields are accessible by setting their visibility correctly and using CSS for styling. This practice not only avoids common errors but also enhances the overall user experience.

By following this guide, you will enhance the functionality of your ASP.NET applications and ensure seamless data retrieval processes. Happy coding!