C# Eval Expression Licensing

For developers who have just purchased a license, it's important to always use the ValidateLicense method to prevent any unexpected issues caused by the trial expired error in your production environment.

Is C# Eval Expression free?

You can use the library for free in the following cases:

  • You only evaluate expressions under 50 characters
  • You use LINQ Dynamic methods

In all other cases, you must purchase a license after evaluating the library.

How long is the evaluation/trial period?

You can evaluate our library for several months before making a purchase.

The trial period stops at the end of the month. However, you can extend the trial by an additional month by downloading the latest version.

How do I purchase a license?

Once you have completed your evaluation, you can purchase the library here.

A few hours after the purchase, you will receive an email with your license name and a license key.

How do I add the license from the appsettings.json file?

You can add the license in an appsettings.json file by creating a new section for our library:

{
  "Z.Expressions.Eval": {
    "LicenseName": "[licenseName]",
    "LicenseKey": "[licenseKey]"
  }
}

NOTE:

  • The name of the JSON file should be exactly appsettings.json (Our library is not aware of any other configuration files).
  • The JSON file should be in the root of the project, not within a folder (Our library is not aware of any other configuration files in other directories).
  • Make sure you still call the ValidateLicense method in your code.

How do I add the license from a config file?

You can add the license directly in an app.config or web.config file in the appSettings section:

<appSettings>
	<add key="Z_Expressions_Eval_LicenseName" value="[licenseName]"/>
	<add key="Z_Expressions_Eval_LicenseKey" value="[licenseKey]"/>
</appSettings>

NOTE:

How do I add the license directly in the code?

The latest way to add the license is by using the AddLicense method directly in the code. The license name and license key can be hardcoded, read from a file, key vault, or any other source:

string licenseName = _configuration["licenseName"]; // or any other technique you usually use to read values from the appsettings.json
string licenseKey = _configuration["licenseKey"]; // // or any other technique you usually use to read values from the appsettings.json

Z.Expressions.EvalManager.AddLicense(licenseName, licenseKey);

string licenseErrorMessage;
if (!Z.Expressions.EvalManager.ValidateLicense(out licenseErrorMessage))
{
    throw new Exception(licenseErrorMessage);
}

NOTE:

  • Make sure to add the license before making the first use of a paid method to ensure it is applied correctly. Otherwise, an error will be thrown.

How can I check if my license is valid?

You should always use the ValidateLicense method. We highly recommend it, as every time someone reported a trial expired error in their production environment, they were not using this method.

The ValidateLicense method allows you to validate that the license has been added correctly. If no license has been added or the license is invalid, the method will return false, and you can retrieve the reason in the licenseErrorMessage variable:

string licenseErrorMessage;
if (!Z.Expressions.EvalManager.ValidateLicense(out licenseErrorMessage))
{
    throw new Exception(licenseErrorMessage);
}

I have a license but received a trial period expired error

The ERROR_005: The monthly trial period has expired... error occurs when the license has not been added correctly to your project.

You can find the most common cause and solution for this issue here. This error can always be avoided by using the ValidateLicense method.

How can I get a free license for Personal or Academic purposes?

We don't offer free licenses.

However, you can use our library for free in your personal or academic projects by downloading the trial at the beginning of every month.

So, technically, you can use it for free for personal or school projects. However, for commercial purposes purchasing a license is always required.

Last updated: 2024-04-11
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