blocks|key|226672|text|这对我来说很有效：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|226673|string+value+=+System.Configuration.ConfigurationManager.AppSettings[key];|code-block|syntax|javascript|226674|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

This works for me:

<pre><code>string value = System.Configuration.ConfigurationManager.AppSettings[key];
</code></pre>

blocks|key|2881530|text|dtsg给出的答案是有效的：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2881531|string+filePath+=+ConfigurationManager.AppSettings["ClientsFilePath"];|code-block|syntax|javascript|2881532|但是，您需要将程序集引用添加到|offset|length|style|BOLD|2881533|2881534|+System.Configuration|blockquote|2881535|2881536|2881537|转到您的解决方案资源管理器，右键单击References并选择Add+reference。选择Assemblies选项卡并搜索配置。|2881538|​|2881539|📷|atomic|2881540|2881541|下面是我的App.config的一个例子|2881542|<?xml+version="1.0"+encoding="utf-8"+?>
<configuration>
++++<startup>+
++++++++<supportedRuntime+version="v4.0"+sku=".NETFramework,Version=v4.5"+/>
++++</startup>
++<appSettings>
++++<add+key="AdminName"+value="My+Name"/>
++++<add+key="AdminEMail"+value="MyEMailAddress"/>
++</appSettings>
</configuration>|2881543|您可以通过以下方式获取：|2881544|string+adminName+=+ConfigurationManager.AppSettings["AdminName"];|2881545|entityMap|0|IMAGE|mutability|IMMUTABLE|imageUrl|https://ask.qcloudimg.com/http-save/yehe-900000/7c495daba02b77d04246c0deddf4d4a9.jpeg|imageAlt^0|0|0|7|5|0|0|0|0|0|0|0|0|1|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|1H|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|1I|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|1J|8|@$I|1K|J|1L|K|L]]|9|@]|A|$]]|$1|M|3|-4|5|6|7|1M|8|@]|9|@]|A|$]]|$1|N|3|O|5|P|7|1N|8|@]|9|@]|A|$]]|$1|Q|3|-4|5|6|7|1O|8|@]|9|@]|A|$]]|$1|R|3|-4|5|6|7|1P|8|@]|9|@]|A|$]]|$1|S|3|T|5|6|7|1Q|8|@]|9|@]|A|$]]|$1|U|3|V|5|6|7|1R|8|@]|9|@]|A|$]]|$1|W|3|X|5|Y|7|1S|8|@]|9|@$I|1T|J|1U|1|1V]]|A|$]]|$1|Z|3|V|5|6|7|1W|8|@]|9|@]|A|$]]|$1|10|3|11|5|6|7|1X|8|@]|9|@]|A|$]]|$1|12|3|13|5|D|7|1Y|8|@]|9|@]|A|$E|F]]|$1|14|3|15|5|6|7|1Z|8|@]|9|@]|A|$]]|$1|16|3|17|5|D|7|20|8|@]|9|@]|A|$E|F]]|$1|18|3|-4|5|6|7|21|8|@]|9|@]|A|$]]]|19|$1A|$5|1B|1C|1D|A|$1E|1F|1G|-4]]]]

The answer that dtsg gave works:

<pre><code>string filePath = ConfigurationManager.AppSettings["ClientsFilePath"];
</code></pre>

BUT, you need to add an assembly reference to

<blockquote>
 System.Configuration
</blockquote>

Go to your Solution Explorer and right click on References and select Add reference. Select the Assemblies tab and search for Configuration.

<img src="https://i.stack.imgur.com/qHQwS.jpg" alt="Reference manager">

Here is an example of my App.config:

<pre><code>&lt;?xml version="1.0" encoding="utf-8" ?&gt;
&lt;configuration&gt;
 &lt;startup&gt; 
 &lt;supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.5" /&gt;
 &lt;/startup&gt;
 &lt;appSettings&gt;
 &lt;add key="AdminName" value="My Name"/&gt;
 &lt;add key="AdminEMail" value="MyEMailAddress"/&gt;
 &lt;/appSettings&gt;
&lt;/configuration&gt;
</code></pre>

Which you can get in the following way:

<pre><code>string adminName = ConfigurationManager.AppSettings["AdminName"];
</code></pre>

blocks|key|228888|text|试一试：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|228889|string+filePath+=+ConfigurationManager.AppSettings["ClientsFilePath"];|code-block|syntax|javascript|228890|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Give this a go:

<pre><code>string filePath = ConfigurationManager.AppSettings["ClientsFilePath"];
</code></pre>

blocks|key|2881624|text|从配置中读取：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2881625|您需要添加一个对Config的引用|2881626|2881627|在项目上打开“属性”|ordered-list-item|2881628|转到“设置”选项卡|2881629|使用以下代码添加"Name“和"+Value+"|2881630|Get+Value+:|2881631|<+code+>G29|2881632|string+value+=+Properties.Settings.Default.keyname;|code-block|syntax|javascript|2881633|保存到配置：|2881634|Properties.Settings.Default.keyName+=+value;
Properties.Settings.Default.Save();|2881635|entityMap^0|0|0|0|0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|10|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|11|8|@]|9|@]|A|$]]|$1|D|3|-4|5|6|7|12|8|@]|9|@]|A|$]]|$1|E|3|F|5|G|7|13|8|@]|9|@]|A|$]]|$1|H|3|I|5|G|7|14|8|@]|9|@]|A|$]]|$1|J|3|K|5|G|7|15|8|@]|9|@]|A|$]]|$1|L|3|M|5|G|7|16|8|@]|9|@]|A|$]]|$1|N|3|O|5|6|7|17|8|@]|9|@]|A|$]]|$1|P|3|Q|5|R|7|18|8|@]|9|@]|A|$S|T]]|$1|U|3|V|5|6|7|19|8|@]|9|@]|A|$]]|$1|W|3|X|5|R|7|1A|8|@]|9|@]|A|$S|T]]|$1|Y|3|-4|5|6|7|1B|8|@]|9|@]|A|$]]]|Z|$]]

Read From Config :

You'll need to add a reference to Config

<ol>
<li>Open "Properties" on your project</li>
<li>Go to "Settings" Tab</li>
<li>Add "Name" and "Value"</li>
<li>Get Value with using following code :</li>
</ol>

<pre class="lang-cs prettyprint-override"><code>string value = Properties.Settings.Default.keyname;
</code></pre>

Save to Config :

<pre><code>Properties.Settings.Default.keyName = value;
Properties.Settings.Default.Save();
</code></pre>

blocks|key|2881401|text|我正在使用：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2881402|++++ExeConfigurationFileMap+configMap+=+new+ExeConfigurationFileMap();
++++//configMap.ExeConfigFilename+=+@"d:\test\justAConfigFile.config.whateverYouLikeExtension";
++++configMap.ExeConfigFilename+=+AppDomain.CurrentDomain.BaseDirectory+%2B+ServiceConstants.FILE_SETTING;
++++Configuration+config+=+ConfigurationManager.OpenMappedExeConfiguration(configMap,+ConfigurationUserLevel.None);
++++value1+=+System.Configuration.ConfigurationManager.AppSettings["NewKey0"];
++++value2+=+config.AppSettings.Settings["NewKey0"].Value;
++++value3+=+ConfigurationManager.AppSettings["NewKey0"];|code-block|syntax|javascript|2881403|其中value1+=+...和value3+=+...提供null，value2+=+...工作|offset|length|style|BOLD|2881404|然后我决定将内部app.config替换为：|2881405|//+Note+works+in+service+but+not+in+wpf
AppDomain.CurrentDomain.SetData("APP_CONFIG_FILE",+@"d:\test\justAConfigFile.config.whateverYouLikeExtension");
ConfigurationManager.RefreshSection("appSettings");

string+value+=+ConfigurationManager.AppSettings["NewKey0"];|2881406|使用VS2012+.net+4|2881407|entityMap^0|0|0|2|C|F|C|Y|C|0|0|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|V|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|W|8|@$I|X|J|Y|K|L]|$I|Z|J|10|K|L]|$I|11|J|12|K|L]]|9|@]|A|$]]|$1|M|3|N|5|6|7|13|8|@]|9|@]|A|$]]|$1|O|3|P|5|D|7|14|8|@]|9|@]|A|$E|F]]|$1|Q|3|R|5|6|7|15|8|@]|9|@]|A|$]]|$1|S|3|-4|5|6|7|16|8|@]|9|@]|A|$]]]|T|$]]

I am using:

<pre><code> ExeConfigurationFileMap configMap = new ExeConfigurationFileMap();
 //configMap.ExeConfigFilename = @"d:\test\justAConfigFile.config.whateverYouLikeExtension";
 configMap.ExeConfigFilename = AppDomain.CurrentDomain.BaseDirectory + ServiceConstants.FILE_SETTING;
 Configuration config = ConfigurationManager.OpenMappedExeConfiguration(configMap, ConfigurationUserLevel.None);
 value1 = System.Configuration.ConfigurationManager.AppSettings["NewKey0"];
 value2 = config.AppSettings.Settings["NewKey0"].Value;
 value3 = ConfigurationManager.AppSettings["NewKey0"];
</code></pre>

Where value1 = ... and value3 = ... gives null and value2 = ... works

Then I decided to replace the internal app.config with:

<pre><code>// Note works in service but not in wpf
AppDomain.CurrentDomain.SetData("APP_CONFIG_FILE", @"d:\test\justAConfigFile.config.whateverYouLikeExtension");
ConfigurationManager.RefreshSection("appSettings");

string value = ConfigurationManager.AppSettings["NewKey0"];
</code></pre>

Using VS2012 .net 4

blocks|key|226834|text|在app/web.config文件中设置以下配置：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|226835|<configuration>
++<appSettings>
++++<add+key="NameForTheKey"+value="ValueForThisKey"+/>
++++...+
++++...++++
++</appSettings>
...
...
</configuration>|code-block|syntax|javascript|226836|然后，您可以在代码中输入以下代码来访问它：|226837|string+myVar+=+System.Configuration.ConfigurationManager.AppSettings["NameForTheKey"];|226838|*请注意，此方法适用于.net4.5.x和.net4.6.x；但不适用于.net+core。最好的问候:拉斐尔|226839|entityMap^0|1|E|0|0|0|0|B|9|L|9|10|9|0^^$0|@$1|2|3|4|5|6|7|S|8|@$9|T|A|U|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|V|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|W|8|@]|D|@]|E|$]]|$1|M|3|N|5|H|7|X|8|@]|D|@]|E|$I|J]]|$1|O|3|P|5|6|7|Y|8|@$9|Z|A|10|B|C]|$9|11|A|12|B|C]|$9|13|A|14|B|C]]|D|@]|E|$]]|$1|Q|3|-4|5|6|7|15|8|@]|D|@]|E|$]]]|R|$]]

In the <code>app/web.config</code> file set the following configuration:

<pre><code>&lt;configuration&gt;
 &lt;appSettings&gt;
 &lt;add key="NameForTheKey" value="ValueForThisKey" /&gt;
 ... 
 ... 
 &lt;/appSettings&gt;
...
...
&lt;/configuration&gt;
</code></pre>

then you can access this in your code by putting in this line:

<pre><code>string myVar = System.Configuration.ConfigurationManager.AppSettings["NameForTheKey"];
</code></pre>

*Note that this work fine for <code>.net4.5.x</code> and <code>.net4.6.x</code>; but do not work for <code>.net core</code>. 
Best regards:
Rafael

blocks|key|2881707|text|很长一段时间后再回到这一点...|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2881708|鉴于ConfigurationManager的消亡，对于任何仍在寻找答案的人，请尝试一下(例如)：|2881709|AppSettingsReader+appsettingsreader+=+new+AppSettingsReader();
string+timeAsString+=+(string)(new+AppSettingsReader().GetValue("Service.Instance.Trigger.Time",+typeof(string)));|code-block|syntax|javascript|2881710|当然，需要System.Configuration。|2881711|(已将代码编辑为实际有效且更易于阅读的内容)|2881712|entityMap^0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|P|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|Q|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|R|8|@]|9|@]|A|$]]|$1|K|3|L|5|6|7|S|8|@]|9|@]|A|$]]|$1|M|3|-4|5|6|7|T|8|@]|9|@]|A|$]]]|N|$]]

Coming back to this one after a long time...

Given the demise of ConfigurationManager, for anyone still looking for an answer to this try (for example):

<pre><code>AppSettingsReader appsettingsreader = new AppSettingsReader();
string timeAsString = (string)(new AppSettingsReader().GetValue("Service.Instance.Trigger.Time", typeof(string)));
</code></pre>

Requires System.Configuration of course.

(Editted the code to something that actually works and is simpler to read)

blocks|key|226780|text|看，我做了我认为显而易见的事情是：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|226781|string+filePath+=+ConfigurationManager.AppSettings.GetValues("ClientsFilePath").ToString();|code-block|syntax|javascript|226782|在编译时，它总是返回null。|226783|然而，这(来自上面)是有效的：|226784|string+filePath+=+ConfigurationManager.AppSettings["ClientsFilePath"];|226785|entityMap^0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|Q|8|@]|9|@]|A|$]]|$1|I|3|J|5|6|7|R|8|@]|9|@]|A|$]]|$1|K|3|L|5|D|7|S|8|@]|9|@]|A|$E|F]]|$1|M|3|-4|5|6|7|T|8|@]|9|@]|A|$]]]|N|$]]

See I did what I thought was the obvious thing was:

<pre><code>string filePath = ConfigurationManager.AppSettings.GetValues("ClientsFilePath").ToString();
</code></pre>

While that compiles it always returns null.

This however (from above) works:

<pre><code>string filePath = ConfigurationManager.AppSettings["ClientsFilePath"];
</code></pre>

blocks|key|3095596|text|有些答案似乎有点偏离IMO这里是我2016年左右的take+|type|unstyled|depth|inlineStyleRanges|offset|length|style|BOLD|entityRanges|data|3095597|<add+key="ClientsFilePath"+value="filepath"/>|code-block|syntax|javascript|3095598|确保引用了System.Configuration。|CODE|3095599|问题是询问应用程序设置密钥的值|3095600|当然，这应该是|3095601|++string+yourKeyValue+=+ConfigurationManager.AppSettings["ClientsFilePath"]

++//yourKeyValue+should+hold+on+the+HEAP++"filepath"|3095602|这里有一个小技巧，你可以把这些值组合在一起(不是这个问题)|3095603|var+emails+=+ConfigurationManager.AppSettings[ConfigurationManager.AppSettings["Environment"]+%2B+"_Emails"];|3095604|emails将是环境键%2B+"_Emails“的值|3095605|example+:+++jack@google.com;thad@google.com;|3095606|entityMap^0|A|3|0|0|5|K|0|B|2|E|1|0|0|0|0|0|0|6|0|0^^$0|@$1|2|3|4|5|6|7|13|8|@$9|14|A|15|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|16|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|17|8|@$9|18|A|19|B|M]]|D|@]|E|$]]|$1|N|3|O|5|6|7|1A|8|@$9|1B|A|1C|B|C]|$9|1D|A|1E|B|C]]|D|@]|E|$]]|$1|P|3|Q|5|6|7|1F|8|@]|D|@]|E|$]]|$1|R|3|S|5|H|7|1G|8|@]|D|@]|E|$I|J]]|$1|T|3|U|5|6|7|1H|8|@]|D|@]|E|$]]|$1|V|3|W|5|H|7|1I|8|@]|D|@]|E|$I|J]]|$1|X|3|Y|5|6|7|1J|8|@$9|1K|A|1L|B|M]]|D|@]|E|$]]|$1|Z|3|10|5|H|7|1M|8|@]|D|@]|E|$I|J]]|$1|11|3|-4|5|6|7|1N|8|@]|D|@]|E|$]]]|12|$]]

Some of the Answers seems a little bit off IMO Here is my take circa 2016 

<pre><code>&lt;add key="ClientsFilePath" value="filepath"/&gt;
</code></pre>

Make sure <code>System.Configuration</code> is referenced.

Question is asking for value of an appsettings key

Which most certainly SHOULD be 

<pre><code> string yourKeyValue = ConfigurationManager.AppSettings["ClientsFilePath"]

 //yourKeyValue should hold on the HEAP "filepath"
</code></pre>

Here is a twist in which you can group together values ( not for this question)

<pre><code>var emails = ConfigurationManager.AppSettings[ConfigurationManager.AppSettings["Environment"] + "_Emails"];
</code></pre>

<code>emails</code> will be value of Environment Key + "_Emails" 

<pre><code>example : jack@google.com;thad@google.com;
</code></pre>

blocks|key|226845|text|对于web应用程序，我通常会编写此方法，并使用键调用它。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|226846|private+String+GetConfigValue(String+key)
++++{
+++++++return+System.Web.Configuration.WebConfigurationManager.AppSettings[key].ToString();
++++}|code-block|syntax|javascript|226847|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

For web application, i normally will write this method and just call it with the key. 

<pre><code>private String GetConfigValue(String key)
 {
 return System.Web.Configuration.WebConfigurationManager.AppSettings[key].ToString();
 }
</code></pre>

blocks|key|3095695|text|您可以简单地键入：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3095696|string+filePath+=+Sysem.Configuration.ConfigurationManager.AppSettings[key.ToString()];|code-block|syntax|javascript|3095697|因为key是一个对象，而AppSettings接受一个字符串|offset|length|style|CODE|3095698|entityMap^0|0|0|2|3|C|B|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|Q|8|@$I|R|J|S|K|L]|$I|T|J|U|K|L]]|9|@]|A|$]]|$1|M|3|-4|5|6|7|V|8|@]|9|@]|A|$]]]|N|$]]

You can simply type: 

<pre><code>string filePath = Sysem.Configuration.ConfigurationManager.AppSettings[key.ToString()];
</code></pre>

because <code>key</code> is an object and <code>AppSettings</code> takes a string

blocks|key|2881719|text|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2881720|在您的项目中打开“属性”|ordered-list-item|2881721|转到“设置”选项卡|2881722|添加“名称”和“值”|2881723|2881724|代码将自动生成|2881725|2881726|+<configuration>+++++++<configSections>+++++++++<sectionGroup+name="applicationSettings"+type="System.Configuration.ApplicationSettingsGroup+..."+...+>+++++++++++<section+name="XX....Properties.Settings"+type="System.Configuration.ClientSettingsSection+..."+...+/>+++++++++</sectionGroup>+++++++</configSections>+++++++<applicationSettings>+++++++++<XX....Properties.Settings>+++++++++++<setting+name="name"+serializeAs="String">+++++++++++++<value>value</value>+++++++++++</setting>+++++++++++<setting+name="name2"+serializeAs="String">+++++++++++++<value>value2</value>+++++++++++</setting>++++++++</XX....Properties.Settings>+++++++</applicationSettings>+++++</configuration>|blockquote|2881727|2881728|获取值的步骤|2881729|Properties.Settings.Default.Name|2881730|或|2881731|Properties.Settings.Default“名称”|2881732|entityMap^0|0|0|0|0|0|0|0|0|0|0|0|0|0^^$0|@$1|2|3|-4|4|5|6|Z|7|@]|8|@]|9|$]]|$1|A|3|B|4|C|6|10|7|@]|8|@]|9|$]]|$1|D|3|E|4|C|6|11|7|@]|8|@]|9|$]]|$1|F|3|G|4|C|6|12|7|@]|8|@]|9|$]]|$1|H|3|-4|4|5|6|13|7|@]|8|@]|9|$]]|$1|I|3|J|4|5|6|14|7|@]|8|@]|9|$]]|$1|K|3|-4|4|5|6|15|7|@]|8|@]|9|$]]|$1|L|3|M|4|N|6|16|7|@]|8|@]|9|$]]|$1|O|3|-4|4|5|6|17|7|@]|8|@]|9|$]]|$1|P|3|Q|4|5|6|18|7|@]|8|@]|9|$]]|$1|R|3|S|4|5|6|19|7|@]|8|@]|9|$]]|$1|T|3|U|4|5|6|1A|7|@]|8|@]|9|$]]|$1|V|3|W|4|5|6|1B|7|@]|8|@]|9|$]]|$1|X|3|-4|4|5|6|1C|7|@]|8|@]|9|$]]]|Y|$]]

<ol>
<li>Open "Properties" on your project</li>
<li>Go to "Settings" Tab</li>
<li>Add "Name" and "Value"</li>
</ol>

CODE WILL BE GENERATED AUTOMATICALLY

<blockquote>
<pre><code> &lt;configuration&gt;
 &lt;configSections&gt;
 &lt;sectionGroup name="applicationSettings" type="System.Configuration.ApplicationSettingsGroup ..." ... &gt;
 &lt;section name="XX....Properties.Settings" type="System.Configuration.ClientSettingsSection ..." ... /&gt;
 &lt;/sectionGroup&gt;
 &lt;/configSections&gt;
 &lt;applicationSettings&gt;
 &lt;XX....Properties.Settings&gt;
 &lt;setting name="name" serializeAs="String"&gt;
 &lt;value&gt;value&lt;/value&gt;
 &lt;/setting&gt;
 &lt;setting name="name2" serializeAs="String"&gt;
 &lt;value&gt;value2&lt;/value&gt;
 &lt;/setting&gt;
 &lt;/XX....Properties.Settings&gt;
 &lt;/applicationSettings&gt;
 &lt;/configuration&gt;
</code></pre>
</blockquote>

To get a value

Properties.Settings.Default.Name

OR

Properties.Settings.Default["name"]

blocks|key|223992|text|ConfigurationManager.RefreshSection("appSettings")
string+value+=+System.Configuration.ConfigurationManager.AppSettings[key];|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|223993|unstyled|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|G|8|@]|9|@]|A|$B|C]]|$1|D|3|-4|5|E|7|H|8|@]|9|@]|A|$]]]|F|$]]

<pre><code>ConfigurationManager.RefreshSection("appSettings")
string value = System.Configuration.ConfigurationManager.AppSettings[key];
</code></pre>

blocks|key|226882|text|或者您可以使用|type|unstyled|depth|inlineStyleRanges|entityRanges|data|226883|string+value+=+system.configuration.ConfigurationManager.AppSettings.Get("ClientsFilePath");

//Gets+the+values+associated+with+the+specified+key+from+the+System.Collections.Specialized.NameValueCollection|code-block|syntax|javascript|226884|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Or you can either use

<pre><code>string value = system.configuration.ConfigurationManager.AppSettings.Get("ClientsFilePath");

//Gets the values associated with the specified key from the System.Collections.Specialized.NameValueCollection
</code></pre>

blocks|key|2881449|text|遵循这里其他答案的建议，我的简单测试也失败了--直到我意识到我添加到桌面应用程序的配置文件被命名为"App1.config“。我将其重命名为"App.config“，一切都立即正常工作。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2881450|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

My simple test also failed, following the advice of the other answers here--until I realized that the config file that I added to my desktop application was given the name "App1.config". I renamed it to "App.config" and everything immediately worked as it ought.

blocks|key|227416|text|已更新|type|unstyled|depth|inlineStyleRanges|entityRanges|data|227417|ConfigurationManager已经过时了，您需要在.NET核心ore环境中使用IConfiguration+(IConfiguration由.NETС内置依赖注入提供)。|227418|++++private+readonly+IConfiguration+config;

++++public+MyConstructor(IConfiguration+config)
++++{
++++++++this.config+=+config;
++++}
++++public+void+DoSomethingFunction()
++++{
++++++++string+settings1+=+config["Setting1"];
++++}|code-block|syntax|javascript|227419|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|L|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|M|8|@]|9|@]|A|$G|H]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

<h1>Updated</h1>
ConfigurationManager is outdated, you need to use IConfiguration in the .NET Сore environment (IConfiguration is provided by .NET Core built-in dependency injection).
<pre><code> private readonly IConfiguration config;

 public MyConstructor(IConfiguration config)
 {
 this.config = config;
 }
 public void DoSomethingFunction()
 {
 string settings1 = config[&quot;Setting1&quot;];
 }
</code></pre>

I'm not able to access values in configuration file.

<pre><code>Configuration config = ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.None);
var clientsFilePath = config.AppSettings.Settings["ClientsFilePath"].Value; 
// the second line gets a NullReferenceException
</code></pre>

.config file:

<pre class="lang-xml prettyprint-override"><code>&lt;?xml version="1.0" encoding="utf-8" ?&gt;
&lt;configuration&gt;
 &lt;appSettings&gt;
 &lt;!-- ... --&gt;
 &lt;add key="ClientsFilePath" value="filepath"/&gt;
 &lt;!-- ... --&gt;
 &lt;/appSettings&gt;
&lt;/configuration&gt;
</code></pre>

Do you have any suggestion what should I do?

AppSettings get value from .config file

我无法访问配置文件中的值。Configuration config = ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.None);var clientsFilePath = config.AppSettings.Settings["ClientsFilePath"].Value; // the second lin

问AppSettings从.config文件获取值
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