System.Xml.XmlBaseWriter.GetQualifiedNamePrefix C# (CSharp) Method

        private string GetQualifiedNamePrefix(string namespaceUri, XmlDictionaryString xNs)
        {
            string prefix = _nsMgr.LookupPrefix(namespaceUri);
            if (prefix == null)
            {
                if (_writeState != WriteState.Attribute)
                    throw System.Runtime.Serialization.DiagnosticUtility.ExceptionUtility.ThrowHelperError(new ArgumentException(SR.Format(SR.XmlNamespaceNotFound, namespaceUri), nameof(namespaceUri)));

                prefix = GeneratePrefix(namespaceUri, xNs);
            }
            return prefix;
        }