Imported Upstream version 4.2.0.179

Former-commit-id: 4610231f55806d2a05ed69e5ff3faa7336cc1479

external/referencesource/System.Configuration/System/Configuration/GenericEnumConverter.cs

@@ -0,0 +1,77 @@
+//------------------------------------------------------------------------------
+// <copyright file="GenericEnumConverter.cs" company="Microsoft">
+//     Copyright (c) Microsoft Corporation.  All rights reserved.
+// </copyright>
+//------------------------------------------------------------------------------
+
+using System;
+using System.Collections;
+using System.IO;
+using System.Reflection;
+using System.Security.Permissions;
+using System.Xml;
+using System.Collections.Specialized;
+using System.Globalization;
+using System.ComponentModel;
+using System.Security;
+using System.Text;
+
+namespace System.Configuration {
+
+    public sealed class GenericEnumConverter : ConfigurationConverterBase {
+        private Type _enumType;
+
+        public GenericEnumConverter(Type typeEnum) {
+            if (typeEnum == null) {
+                throw new ArgumentNullException("typeEnum");
+            }
+
+            _enumType = typeEnum;
+        }
+
+        public override object ConvertTo(ITypeDescriptorContext ctx, CultureInfo ci, object value, Type type) {
+            Debug.Assert(typeof(System.Enum).IsAssignableFrom(value.GetType()), "typeof(System.Enum).IsAssignableFrom(value.GetType())");
+
+            return value.ToString();
+        }
+        
+        public override object ConvertFrom(ITypeDescriptorContext ctx, CultureInfo ci, object data) {
+            object result = null;
+            //
+            // For any error, throw the ArgumentException with SR.Invalid_enum_value
+            //
+            try {
+                string value = (string)data;
+                if (String.IsNullOrEmpty(value)) {
+                    throw new Exception();
+                }
+
+                // Disallow numeric values for enums.
+                if (!String.IsNullOrEmpty(value) &&
+                        (Char.IsDigit(value[0]) ||
+                        (value[0] == '-') ||
+                        (value[0] == '+'))) {
+                    throw new Exception();
+                }
+
+                if (value != value.Trim()) { // throw if the value has whitespace 
+                    throw new Exception();
+                }
+
+                result = Enum.Parse(_enumType, value);
+            }
+            catch {
+                StringBuilder names = new StringBuilder();
+
+                foreach (string name in Enum.GetNames(_enumType)) {
+                    if (names.Length != 0) {
+                        names.Append(", ");
+                    }
+                    names.Append(name);
+                }
+                throw new ArgumentException(SR.GetString(SR.Invalid_enum_value, names.ToString()));
+            }
+            return result;
+        }
+    }
+}