This class is a dictionary collection in which keys and values are all strings.

public class StringDictionary : IEnumerable {
// Public Constructors
   public StringDictionary( );
// Public Instance Properties
   public virtual int Count{get; }
   public virtual bool IsSynchronized{get; }
   public virtual ICollection Keys{get; }
   public virtual object SyncRoot{get; }
   public virtual string this[string key]{set; get; }
   public virtual ICollection Values{get; }
// Public Instance Methods
   public virtual void Add(string key, string value);
   public virtual void Clear( );
   public virtual bool ContainsKey(string key);
   public virtual bool ContainsValue(string value);
   public virtual void CopyTo(Array array, int index);
   public virtual IEnumerator GetEnumerator( );        
// implements IEnumerable
   public virtual void Remove(string key);
}

Returned By

System.Diagnostics.ProcessStartInfo.EnvironmentVariables