System.Xml.Serialization.XmlSchemaExporter.ExportDefaultValue C# (CSharp) Method

        static internal string ExportDefaultValue(TypeMapping mapping, object value)
        {
            if (!(mapping is PrimitiveMapping))
                // should throw, but it will be a breaking change;
                return null;

            if (value == null || value == DBNull.Value)
                return null;

            if (mapping is EnumMapping)
            {
                EnumMapping em = (EnumMapping)mapping;

#if DEBUG
                    // use exception in the place of Debug.Assert to avoid throwing asserts from a server process such as aspnet_ewp.exe
                    if (value.GetType() != typeof(string)) throw new InvalidOperationException(SR.Format(SR.XmlInternalErrorDetails, SR.Format(SR.XmlInvalidDefaultValue, value.ToString(), value.GetType().FullName)));
#endif

                // check the validity of the value
                ConstantMapping[] c = em.Constants;
                if (em.IsFlags)
                {
                    string[] names = new string[c.Length];
                    long[] ids = new long[c.Length];
                    Hashtable values = new Hashtable();
                    for (int i = 0; i < c.Length; i++)
                    {
                        names[i] = c[i].XmlName;
                        ids[i] = 1 << i;
                        values.Add(c[i].Name, ids[i]);
                    }
                    long val = XmlCustomFormatter.ToEnum((string)value, values, em.TypeName, false);
                    return val != 0 ? XmlCustomFormatter.FromEnum(val, names, ids, mapping.TypeDesc.FullName) : null;
                }
                else
                {
                    for (int i = 0; i < c.Length; i++)
                    {
                        if (c[i].Name == (string)value)
                        {
                            return c[i].XmlName;
                        }
                    }
                    return null; // unknown value
                }
            }

            PrimitiveMapping pm = (PrimitiveMapping)mapping;

            if (!pm.TypeDesc.HasCustomFormatter)
            {
#if DEBUG
                    // use exception in the place of Debug.Assert to avoid throwing asserts from a server process such as aspnet_ewp.exe
                    if (pm.TypeDesc.Type == null) {
                        throw new InvalidOperationException(SR.Format(SR.XmlInternalErrorDetails, "Mapping for " + pm.TypeDesc.Name + " missing type property"));
                    }
#endif

                if (pm.TypeDesc.FormatterName == "String")
                    return (string)value;

                Type formatter = typeof(XmlConvert);
                System.Reflection.MethodInfo format = formatter.GetMethod("ToString", new Type[] { pm.TypeDesc.Type });
                if (format != null)
                    return (string)format.Invoke(formatter, new Object[] { value });
            }
            else
            {
                string defaultValue = XmlCustomFormatter.FromDefaultValue(value, pm.TypeDesc.FormatterName);
                if (defaultValue == null)
                    throw new InvalidOperationException(SR.Format(SR.XmlInvalidDefaultValue, value.ToString(), pm.TypeDesc.Name));
                return defaultValue;
            }
            throw new InvalidOperationException(SR.Format(SR.XmlInvalidDefaultValue, value.ToString(), pm.TypeDesc.Name));
        }