Using Environment Variables

Simple Configuration

You can add environment variables to your variable collection as follows:

Note

The optional first parameter allows for filtering of environment variables. In this case we are only matching the environment variable that we set up.

The optional prefix used in this example is ENV_. This is the default prefix and the parameter could have been omitted in this instance

Warning

If the ITransformer that is used for the variable replacer cannot handle an environment variable's name then the environment variable will be ignored. This behaviour can be overriden as seen here

Environment.SetEnvironmentVariable("NAME", "Als");

var replacer = new VariableReplacerFactory()
    .Build(c => c
        .AddEnvironmentVariables(key => key == "NAME", prefix: "ENV_"));

var result = replacer.ReplaceVariables("Hi $(ENV_NAME)");

// result will be "Hi Als"

Advanced Configuration

An overload of the AddEnvironmentVariables method allows for further control of how we select environment variables.

The following example shows us disabling the automatic filtering of environment variables if their name is not valid for the ITransformer in use.

Note

There may be scenarios whereby this is desirable in order to check what variables are being added and which ones are problematic via the exception that is thrown at the point of an IVariableReplacer being created.

// This environment variable's key has a '-' in it 
// and the default transformer does not allow this.
Environment.SetEnvironmentVariable("ALS-NAME", "Als");

// This will throw an InvalidVariableNamesException with a message 
// that will show the problematic environment variables
var replacer = new VariableReplacerFactory()
    .Build(c => c
        .AddEnvironmentVariables(c => c
            .DisableInvalidVariableNameFilter()
            .WithEnvironmentVariableFilter(_ => true)
            .WithPrefix("MyPrefix_")));