92 lines
3.8 KiB
C#
92 lines
3.8 KiB
C#
//------------------------------------------------------------------------------
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// <copyright file="AppSettingsReader.cs" company="Microsoft">
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// Copyright (c) Microsoft Corporation. All rights reserved.
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// </copyright>
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//------------------------------------------------------------------------------
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using System;
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using System.Reflection;
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using System.Configuration;
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using System.Collections.Specialized;
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using System.Globalization;
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namespace System.Configuration {
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/// <devdoc>
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/// The AppSettingsReader class provides a wrapper for System.Configuration.ConfigurationManager.AppSettings
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/// which provides a single method for reading values from the config file of a particular type.
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/// </devdoc>
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public class AppSettingsReader {
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private NameValueCollection map;
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static Type stringType = typeof(string);
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static Type[] paramsArray = new Type[] { stringType };
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static string NullString = "None";
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/// <devdoc>
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/// Constructor
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/// </devdoc>
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public AppSettingsReader() {
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map = System.Configuration.ConfigurationManager.AppSettings;
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}
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/// <devdoc>
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/// Gets the value for specified key from ConfigurationManager.AppSettings, and returns
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/// an object of the specified type containing the value from the config file. If the key
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/// isn't in the config file, or if it is not a valid value for the given type, it will
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/// throw an exception with a descriptive message so the user can make the appropriate
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/// change
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/// </devdoc>
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public object GetValue(string key, Type type) {
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if (key == null) throw new ArgumentNullException("key");
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if (type == null) throw new ArgumentNullException("type");
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string val = map[key];
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if (val == null) throw new InvalidOperationException(SR.GetString(SR.AppSettingsReaderNoKey, key));
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if (type == stringType) {
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// It's a string, so we can ALMOST just return the value. The only
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// tricky point is that if it's the string "(None)", then we want to
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// return null. And of course we need a way to represent the string
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// (None), so we use ((None)), and so on... so it's a little complicated.
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int NoneNesting = GetNoneNesting(val);
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if (NoneNesting == 0) {
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// val is not of the form ((..((None))..))
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return val;
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}
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else if (NoneNesting == 1) {
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// val is (None)
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return null;
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}
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else {
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// val is of the form ((..((None))..))
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return val.Substring(1, val.Length - 2);
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}
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}
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else {
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try {
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return Convert.ChangeType(val, type, CultureInfo.InvariantCulture);
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} catch (Exception) {
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string displayString = (val.Length == 0) ? SR.AppSettingsReaderEmptyString : val;
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throw new InvalidOperationException(SR.GetString(SR.AppSettingsReaderCantParse, displayString, key, type.ToString()));
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}
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}
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}
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private int GetNoneNesting(string val) {
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int count = 0;
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int len = val.Length;
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if (len > 1) {
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while (val[count] == '(' && val[len - count - 1] == ')') {
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count++;
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}
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if (count > 0 && string.Compare(NullString, 0, val, count, len - 2 * count, StringComparison.Ordinal) != 0) {
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// the stuff between the parens is not "None"
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count = 0;
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}
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}
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return count;
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}
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}
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}
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