System.Xml.XmlConvert.VerifyNCName C# (CSharp) Method

        internal static string VerifyNCName(string name, ExceptionType exceptionType)
        {
            if (name == null)
            {
                throw new ArgumentNullException(nameof(name));
            }
            if (name.Length == 0)
            {
                throw new ArgumentNullException(nameof(name), SR.Xml_EmptyLocalName);
            }

            int end = ValidateNames.ParseNCName(name, 0);

            if (end != name.Length)
            {
                // If the string is not a valid NCName, then throw or return false
                throw CreateInvalidNameCharException(name, end, exceptionType);
            }

            return name;
        }

        internal void WriteQualifiedNameInternal(string localName, string ns)
        {
            if (localName == null || localName == String.Empty)
            {
                throw new ArgumentException();
            }
            if (ns == null)
            {
                ns = String.Empty;
            }

#if NET_2_0
            if (Settings != null)
            {
                switch (Settings.ConformanceLevel)
                {
                case ConformanceLevel.Document:
                case ConformanceLevel.Fragment:
                    XmlConvert.VerifyNCName(localName);
                    break;
                }
            }
            else
            {
                XmlConvert.VerifyNCName(localName);
            }
#else
            XmlConvert.VerifyNCName(localName);
#endif

            string prefix = ns.Length > 0 ? LookupPrefix(ns) : String.Empty;
            if (prefix == null)
            {
                throw new ArgumentException(String.Format("Namespace '{0}' is not declared.", ns));
            }

            if (prefix != String.Empty)
            {
                WriteString(prefix);
                WriteString(":");
                WriteString(localName);
            }
            else
            {
                WriteString(localName);
            }
        }