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Learn how to effectively utilize LINQ's FirstOrDefault method to get multiple values from a comma separated list in C# .
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How to Retrieve Comma Separated Multiple Values Using FirstOrDefault in LINQ Queries

When working with data in C# , it’s common to face challenges when dealing with multiple values from a database or a JSON structure. One particular scenario you might encounter is trying to retrieve values from a comma-separated string and map them to their corresponding entities in a LINQ query.

In this post, we will explore a method to resolve the issue of fetching multiple city names from a comma-separated list using LINQ's FirstOrDefault() feature.

The Problem

Imagine you have a list of city names that are stored as a single string, for example: HYD,MUM. You encounter a problem when trying to extract these values, especially when your cities might come from a JSON structure, leading to errors such as "FirstOrDefault error".

Example Input

You have a class defined as follows:

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

And here's an example of a JSON object converted into a C# list:

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

You’re attempting to extract city names, but only the first match appears using FirstOrDefault(). Here’s the issue in your current code:

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

The Solution

To effectively retrieve multiple values from a list, we will break down the solution into a few clear steps.

Step 1: Split the Comma-Separated String

First, you need to split the cities string into a list of individual city codes. This can be done using the Split method. You can store these results in a List<string> for further processing.

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

Step 2: Use Contains with FirstOrDefault()

Next, instead of directly using the FirstOrDefault() method, you would leverage the Contains() method to determine if the SelectedValue exists in your list of city codes. Here’s how you can achieve this:

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

Complete Example

Combining all the steps, your final code would look like this:

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

Conclusion

By breaking down the problem and using the Contains() method in conjunction with the Split() function, you can effortlessly retrieve multiple values from a comma-separated string. This not only resolves the error frequently encountered with FirstOrDefault() in LINQ queries but also enhances the efficiency of your data retrieval process.

Now, you should be able to comfortably manipulate city data and other similar structured information in your projects. Happy coding!