Passing variable params to another variable params

March 15, 2023

I want to pass a params object from my method to another methods params object like the following, but I cannot figure out the syntax, or if it is even possible.

readonly ILogger<T> _logger;
readonly string _businessUnit = "Marketing";

private void LogTheThing(string message, params object?[] args) {
  _logger.LogInformation($"{{BusinessUnit}} - {message}", _businessUnit, args);
}

public void Go() {
  LogTheThing($"{{OrderId}} - Could not locate your order. Try searching for {{ExternalOrderId}}", 45623, "A987BZ1");
}

Currently when I pass LogTheThing‘s args to the ILogger‘s args, the array of objects from my method winds up in the first array element of the Ilogger‘s args.

I tried these with no luck:

_logger.LogInformation($"{{BusinessUnit}} - {message}", _businessUnit, args.ToArray()); // nope
_logger.LogInformation($"{{BusinessUnit}} - {message}", _businessUnit, args.ToList()); // nope

This example actually shows the unwanted – default behavior.

Is it possible to "spread" my args and have c# treat it as:

_logger.LogInformation($"{{BusinessUnit}} - {message}", _businessUnit, args[0], args[1], arg[x]...);

>Solution :

Basically you’d need to create an array containing both _businessUnit and all the args contents:

object[] newArgs = new object[args.Length + 1];
newArgs[0] = _businessUnit;
Array.Copy(args, 0, newArgs, 1, args.Length);
_logger.LogInformation($"{{BusinessUnit}} - {message}", newArgs);

There’s nothing built into C# as a language to do that.