Скачать или смотреть Resolving the System.Linq.Dynamic.Core Object Type Comparison Issue in C#

Discover how to effectively manage object type comparisons in dynamic LINQ queries and avoid common pitfalls with practical examples and solutions.
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This video is based on the question https://stackoverflow.com/q/64797434/ asked by the user 'Justinus Hermawan' ( https://stackoverflow.com/u/3087119/ ) and on the answer https://stackoverflow.com/a/64797603/ provided by the user 'David L' ( https://stackoverflow.com/u/1165998/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Resolving the System.Linq.Dynamic.Core Object Type Comparison Issue in C#

When working with dynamic queries in C# , developers often encounter various challenges. One common problem arises when attempting to compare types in dynamic LINQ queries, particularly when dealing with object types. In this guide, we will explore how to overcome the System.InvalidOperationException that occurs when trying to compare an object type with other types like Int32.

Understanding the Problem

The Setup

Suppose we have the following model defined:

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And we create a sample dataset as follows:

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However, running this code will lead to the following exception:

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This occurs because comparing object types directly with specific types like Int32 isn't allowed without proper type casting in C# .

The Solution

Using .Equals()

To resolve the comparison error, you can utilize the .Equals() method, which allows for safer comparisons by first checking type identity before executing the comparison. Here’s how you can do it:

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Potential Pitfalls with .Equals()

While using .Equals() can prevent the aforementioned exception, there are a few caveats:

Null References: If the left-hand side of the .Equals() is null, it will throw a NullReferenceException. Therefore, it's essential to ensure the variable being compared is not null.

Strongly Typed Alternatives

While the above solutions can work, they may not be the best practice. A better and more robust approach would be to use a strongly typed data structure. Here’s how you can redefine the model using a ValueTuple, which will allow for direct comparison without needing object types:

Revised Model Definition

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Sample Data with Strongly Typed Values

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Benefits of this Approach

Type Safety: Reduces runtime errors related to type mismatches.

No Null Handling: Since tuples are strongly typed, they are less prone to null-related exceptions.

Performance: Avoids boxing and casting operations, leading to better performance.

Conclusion

In this post, we explored the System.InvalidOperationException problem when using dynamic LINQ queries with object types and provided several solutions, ranging from safer method uses to adopting strongly typed structures. By implementing these strategies, you can write more reliable and maintainable code while avoiding common pitfalls related to type comparisons in C# .