C# Eval Expression - Licensing

Evaluation Period

You can evaluate our library for several months before purchasing it.

The trial period stops at the end of the month. When you receive a license expiration error, download the latest version which will automatically extend your trial period.

You can also purchase the library here

Upon purchase, you will receive a license name and a license key.

Setup License from config file

The license name and key can be directly be added in the app.config or web.config file in the appSettings section.


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

Setup License from code

You can also set the license name and key directly in the code.


// using Z.Expressions; // Don't forget to include this.

string licenseName = //... PRO license name
string licenseKey = //... PRO license key

EvalManager.AddLicense(licenseName, licenseKey);


  • Use the config file to store your license name and license key.
  • Web App: Use Application_Start in global.asax to activate your license.
  • WinForm App: Use the main thread method to activate your license.
  • Win Service: Use the OnStart method to activate your license

The AddLicense must always be set before the first call to the library. Otherwise, you will start the evaluation period

How can I check if my license is valid?

The validate method allow you to know whether your license is valid or not.


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