/// <summary>
        /// Tries the select read only variable at random.
        /// </summary>
        /// <returns><c>true</c>, if select read only variable at random was tryed, <c>false</c> otherwise.</returns>
        /// <param name="returnType">Return type.</param>
        /// <param name="signatureOut">Signature out.</param>
        public static bool TrySelectReadOnlyVariableAtRandom(
            Type returnType,
            out VariableSignature signatureOut)
        {
            if (readOnlyVariableList == null)
            {
                throw new InvalidOperationException("readOnlyVariableList is null");
            }

            List <VariableSignature> candidates = new List <VariableSignature> ();

            foreach (VariableSignature signature in readOnlyVariableList)
            {
                if (signature.VariableType == returnType)
                {
                    candidates.Add(signature);
                }
            }

            foreach (VariableSignature signature in readWriteVariableList)
            {
                if (signature.VariableType == returnType)
                {
                    candidates.Add(signature);
                }
            }

            if (candidates.Count == 0)
            {
                signatureOut = null;
                return(false);
            }

            int index = CommonHelperMethods.GetRandomPositiveInt0ToValue(candidates.Count - 1);

            signatureOut = candidates [index];
            return(true);
        }
        /// <summary>
        /// Adds a read write variable.
        /// </summary>
        /// <param name="signature">Signature.</param>
        public static void AddReadWriteVariable(EntVariableEnum variableId, Type variableType)
        {
            VariableSignature signature = new VariableSignature(variableId, variableType);

            readWriteVariableList.Add(signature);
        }