You can add the parameters after the invoke:
Action<string> d = RefreshTextBoxResults;
this.Invoke(d, profileString + "\n");
Or invoke an action where the parameter is already included (which is this case is suitable regarding re usability)
Action d= () =>RefreshTextBoxResults(profileString + "\n");
if (this.InvokeRequired)
{
Invoke(d);
}
else
{
d();
}
PS, if you want to use your RefreshTextBox delegate instead of an Action, the RefreshTextBox delegate should be altered to include a string parameter