System.Xml.XmlBaseWriter.NamespaceManager.AddNamespace C# (CSharp) Method

            public void AddNamespace(string prefix, string uri, XmlDictionaryString uriDictionaryString)
            {
                if (prefix.Length >= 3)
                {
                    // Upper and lower case letter differ by a bit.
                    if ((prefix[0] & ~32) == 'X' && (prefix[1] & ~32) == 'M' && (prefix[2] & ~32) == 'L')
                    {
                        if (prefix == "xml" && uri == xmlNamespace)
                            return;
                        if (prefix == "xmlns" && uri == xmlnsNamespace)
                            return;
                        throw System.Runtime.Serialization.DiagnosticUtility.ExceptionUtility.ThrowHelperError(new ArgumentException(SR.Format(SR.XmlReservedPrefix), nameof(prefix)));
                    }
                }
                Namespace nameSpace;
                for (int i = _nsCount - 1; i >= 0; i--)
                {
                    nameSpace = _namespaces[i];
                    if (nameSpace.Depth != _depth)
                        break;
                    if (nameSpace.Prefix == prefix)
                    {
                        if (nameSpace.Uri == uri)
                            return;
                        throw System.Runtime.Serialization.DiagnosticUtility.ExceptionUtility.ThrowHelperError(new ArgumentException(SR.Format(SR.XmlPrefixBoundToNamespace, prefix, nameSpace.Uri, uri), nameof(prefix)));
                    }
                }
                if (prefix.Length != 0 && uri.Length == 0)
                    throw System.Runtime.Serialization.DiagnosticUtility.ExceptionUtility.ThrowHelperError(new ArgumentException(SR.Format(SR.XmlEmptyNamespaceRequiresNullPrefix), nameof(prefix)));
                if (uri.Length == xmlnsNamespace.Length && uri == xmlnsNamespace)
                    throw System.Runtime.Serialization.DiagnosticUtility.ExceptionUtility.ThrowHelperError(new ArgumentException(SR.Format(SR.XmlSpecificBindingNamespace, "xmlns", uri)));
                // The addressing namespace and the xmlNamespace are the same length, so add a quick check to try to disambiguate
                if (uri.Length == xmlNamespace.Length && uri[18] == 'X' && uri == xmlNamespace)
                    throw System.Runtime.Serialization.DiagnosticUtility.ExceptionUtility.ThrowHelperError(new ArgumentException(SR.Format(SR.XmlSpecificBindingNamespace, "xml", uri)));

                if (_namespaces.Length == _nsCount)
                {
                    Namespace[] newNamespaces = new Namespace[_nsCount * 2];
                    Array.Copy(_namespaces, 0, newNamespaces, 0, _nsCount);
                    _namespaces = newNamespaces;
                }
                nameSpace = _namespaces[_nsCount];
                if (nameSpace == null)
                {
                    nameSpace = new Namespace();
                    _namespaces[_nsCount] = nameSpace;
                }
                nameSpace.Depth = _depth;
                nameSpace.Prefix = prefix;
                nameSpace.Uri = uri;
                nameSpace.UriDictionaryString = uriDictionaryString;
                _nsCount++;
                _lastNameSpace = null;
            }