Mastering .NET Core Fluent Validation: Accepting Empty or Precise Decimal Values

Описание: Learn how to effectively implement `.NET Core` Fluent Validation to allow for empty decimal fields or enforce a precision of `1,4` on given values.
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This video is based on the question https://stackoverflow.com/q/62689302/ asked by the user 'Niranjan godbole' ( https://stackoverflow.com/u/4898395/ ) and on the answer https://stackoverflow.com/a/62689970/ provided by the user 'Arsalan Valoojerdi' ( https://stackoverflow.com/u/10310353/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Understanding Fluent Validation in .NET Core

When developing applications in .NET Core, validation of user input is a crucial part of ensuring data integrity. As developers, we often encounter fields that may or may not contain values, particularly with decimal numbers. One example is when you need to validate a decimal field that can be either empty or must adhere to a certain precision.

In this guide, we will tackle a specific challenge: how to validate a decimal field in .NET Core using Fluent Validation so that it meets a set of defined rules.

The Challenge

The scenario we are dealing with involves validating a Mast Height decimal field in our model. Here are the validation rules that need to be addressed:

Mast Height cannot be null.

Mast Height may be empty.

Mast Height can take a value of zero.

If a value is present, it must adhere to the precision of 1,4 (1 digit before the decimal point and 4 digits after).

The initial approach taken was incorrect, and developers often face similar hurdles. Our goal is to provide a clear and functional solution that adheres to these requirements.

Implementing the Solution

To effectively validate the Mast Height field under the specified rules, we will modify our Fluent Validation code. Below is the correct implementation:

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

Breakdown of the Code

RuleFor(p = p.MastHeight): This begins the validation chain by targeting the MastHeight property in our model.

ScalePrecision(1, 4): This method sets the precision rules for the decimal. It expects up to 1 digit before the decimal point and up to 4 digits after the decimal point, aligning with the precision requirement.

When(p = p.MastHeight != decimal.Zero && p.MastHeight.HasValue): This condition ensures that the scale and precision rules are only applied when the Mast Height has a value and is not equal to zero. This neatly complies with our requirement that the field can also be empty.

Additional Notes

Here are a few considerations to remember when using Fluent Validation:

Chaining Rules: Fluent Validation allows for chaining various validation rules together, which helps in building complex rules in a readable manner.

Testing Validations: Always test your validations thoroughly to ensure that all edge cases—such as null, empty, and valid/invalid decimal values—are correctly managed.

Flexibility: Fluent Validation is highly flexible, allowing you to create custom rules and conditions based on your specific requirements.

Conclusion

By systematically applying these steps, you can effectively manage the validation of decimal fields in your .NET Core applications using Fluent Validation. The combination of ensuring that the field can either be empty or must adhere to strict precision not only improves data quality but also enhances the user experience.

Feel free to share your experiences or ask questions regarding Fluent Validation below. Your input is valued and contributes to a vibrant developer community. Happy coding!