Assuming you have a people editor control defined like below:
<wssawc:PeopleEditor AllowEmpty="false" ID="myPeopleEditorControl" runat=server SelectionSet="User" MaximumEntities="1" MultiSelect="false" AllowTypeIn="false" Width='500px' />
The following code sample will get you the currently logged on user's login from the PeopleEditor control:
ArrayList peEntities = myPeopleEditorControl.Entities;
PickerEntity pickEn = (PickerEntity)peEntities[0];
stringLogIn = pickEn.Key;
This comes handy when you want to create an SPUser context out of the entities kept in the PeopleEditor control. For example:
private SPUser GetUser(string logIn)
{
SPUser user = this.workflowProperties.Web.SiteUsers[logIn];
return user;
}
Don't forget Required Field Validation on your people editor control if you want the code not to break on you.