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I want to get different tags of App.config File in C#

I have to get string inside Setting-> Value in C#. How to reach there through code and fetch that value from App.config file. Please help me. Thank you.
<?xml version="1.0" encoding="utf-8" ?>
<configuration>
<configSections>
<sectionGroup name="applicationSettings" type="System.Configuration.ApplicationSettingsGroup, System, Version=4.0.0.0,Culture=neutral, PublicKeyToken=b77a5c561934e089" >
<section name="MyApplication.Properties.Settings" type="System.Configuration.ClientSettingsSection, System, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" requirePermission="false" />
</sectionGroup>
</configSections>
<startup>
<supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.5" />
</startup>
<applicationSettings>
<MyApplication.Properties.Settings>
**<setting name="ConnectionString" serializeAs="String">
<value>server=127.0.0.1;uid=root;pwd=root;database=MyApplication_db;</
</setting>**
</VASI_Application.Properties.Settings>
</applicationSettings>
</configuration>

You can use the following code:
var section = (ClientSettingsSection)ConfigurationManager.GetSection("applicationSettings/MyApplication.Properties.Settings");
var settingElement = section.Settings.Get("ConnectionString");
var settingValue = settingElement.Value.ValueXml.InnerText;
// settingValue equals "server=127.0.0.1;uid=root;pwd=root;database=MyApplication_db;"
First, you retrieve the ClientSettingsSection section. The name of the section is a combination of the name of the "applicationSettings" section and its inner "MyApplication.Properties.Settings" section. Then, you retrieve the actual settings by calling Settings.Get("ConnectionString") on the returned ClientSettingsSection instance. Finally, you can use the Value.ValueXml.InnerText property of the returned setting to get to the actual value.
By the way, you have two small errors in your XML file:
The <MyApplication.Properties.Settings> element in incorrectly closed with </VASI_Application.Properties.Settings>
The <value> element is not correctly closed with </value>

Don't you have the property ConnectionString?
As documented here, usually you can access it in this way:
var setting = Properties.Settings.Default.ConnectionString;
By the way, your application tag starts with MyApplication.Properties.Settings but ends with VASI_Application.Properties.Settings

If you do actually want to go ahead with a custom config file section like in your example then you will need to follow this Microsoft guide for creating custom configuration sections.
https://msdn.microsoft.com/en-us/library/2tw134k3.aspx
If you get stuck following this guide then raise another question.

"Configuration system failed to initialize" error

I'm getting this exception when using the code:
var appSettings = ConfigurationManager.AppSettings; //Exception here
string result = appSettings["ILFSsqlServer"] ?? "Not Found"; //trying to get to this point
I'm not really sure why and from previous answers to this question I think I'm doing exactly what they suggest but to no avail.
My app.config is:
<?xml version="1.0"?>
<configuration>
<configSections>
<sectionGroup name="userSettings"
type="System.Configuration.UserSettingsGroup, System, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" >
</sectionGroup>
</configSections>
<AppSettings>
<add key="ILFSsqlServer" value="ODBC;DSN=sql server copycloas;Trusted_Connection=Yes;APP=Microsoft Office 2010;DATABASE=ILFSView;"/>
</AppSettings>
</configuration>

On your app.config you should write appSettings, lowercase A.

Tell ConfigurationManager to ignore App.config section

My App.config file is markuped as:
<configuration>
<configSections>
<section name="Custom" type="…" />
</configSections>
<Custom>
...
</Custom>
<Ignored>
...
</Ignored>
</configuration>
So, I have an configuration file, where:
one section ("Custom") is handled by API and I have written ConfigurationSection inheritor for it
second section ("Ignored") I will parse by myself, because Configuration API doesnt let me solve my task.
When I run program, exception occurs "Unrecognized configuration section 'Ignored'".
Do I have possibility to tell ConfigurationManager to ignore this section "Ignored"?

You can add the following to your <configSections> element:
<section name="Ignored" type="System.Configuration.IgnoreSection, System.Configuration, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a" />

Storing settings in configFile

Try to save all data in to config file, and then read it and apply to my program during running - as user preference.
Whats done: create new config file (using Add new element-> add congif file). In this file put simple code
<?xml version="1.0" encoding="utf-8" ?>
<configuration>
<appSetting>
<add Key="Volume" value="100" />
</appSetting>
</configuration>
After it create method
public int GetVolumeFromConfigFile()
{
return Convert.ToInt32(ConfigurationManager.AppSettings.Get("Volume"));
}
and in main programm call it like
Value = (MyClass.GetVolumeFromConfigFile());
But it's not work. (During debaggin it's return nothing)
Think it can be few reason:
I need to add (I don't now in what way) what config file to use, because i have few files *.config - one as default (App.exe.config, and another - that i created)
I use incorrect method to get value from config file
Also I read about some another way to store app settings, like store it in *.settings file
What I'm doing wrong and what method prefered?
Additional information - use net 4.0
EDIT
Remove my config file, and add to existed few lines (in strong>)
<?xml version="1.0" encoding="utf-8" ?>
<configuration>
<configSections>
<sectionGroup name="userSettings" type="System.Configuration.UserSettingsGroup, System, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" >
<section name="PlayDemo.SettingsPlayIt" type="System.Configuration.ClientSettingsSection, System, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" allowExeDefinition="MachineToLocalUser" requirePermission="false" />
</sectionGroup>
</configSections>
<startup>
<supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.5" />
</startup>
<userSettings>
<PlayDemo.SettingsPlayIt>
<setting name="Volume" serializeAs="String">
<value>10</value>
</setting>
</PlayDemo.SettingsPlayIt>
</userSettings>
Here I add my key
<appSetting>
<add key="Volume" value="100" />
</appSetting>
</configuration>

try this:
<?xml version="1.0" encoding="utf-8" ?>
<configuration>
<appSettings>
<add key="Volume" value="100" />
</appSettings>
</configuration>
and
return Convert.ToInt32(ConfigurationManager.AppSettings["Volume"]);
the appSettings are key value pairs, so you can access it like you would a value in a Dictionary

If you want to use a separate config file, try this:
Dim config As System.Configuration.Configuration = ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.None)
config.AppSettings.File = "yourFileName"'tell Configuration what file to read
config.Save(ConfigurationSaveMode.Modified) ' save the Configuration setting
ConfigurationManager.RefreshSection("appSettings") ' update just the <appSettings> node

I really like the following technique, using ConfigurationSection. This allows you for painless manipulation of your configuration. But it is more specific upfront.
http://msdn.microsoft.com/en-us/library/2tw134k3%28v=vs.90%29.aspx

App.config - custom section not working

I recently started building a console version of a web application. I copied my custom sections from my web.config. to my app.config. When I go to get config information i get this error:
An error occurred creating the configuration section handler for x/y: Could not load type 'x' from assembly 'System.Configuration
The line that it is not liking is:
return ConfigurationManager.GetSection("X/Y") as Z;
Anyone run into something like this?
I was able to add
<add key="IsReadable" value="0"/>
in the appSettings and read it.
Addition:
I do actually have this defined about the custom section:
<configSections>
<sectionGroup name="x">
<section name="y" type="zzzzz"/>
</sectionGroup>
</configSections>

it sounds like your config-section handler is not defined
<configSection>
<section
name="YOUR_CLASS_NAME_HERE"
type="YOUR.NAMESPACE.CLASSNAME, YOUR.NAMESPACE, Version=1.1.0.0, Culture=neutral, PublicKeyToken=PUBLIC_TOKEN_ID_FROM_ASSEMBLY"
allowLocation="true"
allowDefinition="Everywhere"
/>
</configSection>

I had this identical issue recently. I created a custom sectiongroup for a web application(ran just fine), but when I ported this layer to a console app, the sectiongroup was failing.
You were correct in your question regarding how much of the "type" is required in your section definition. I've modified your configuration section with an example below:
<configSection>
<section
name="yourClassName"
type="your.namespace.className, your.assembly"
allowLocation="true"
allowDefinition="Everywhere" />
</configSection>
You'll notice, the type now has class name followed by assembly name. This is required for interaction outside of a web environment.
NOTE: Assembly name does not necessarily equal your namespace(for a given section).

If you want a custom config handler you have to define the class and reference it as shown by Steven Lowe. You can inherit from predefined handlers, or you can just use the value/key pair that is offered in appSetting section as you noted.

At the top of your file you require to have configSection tag with inside the section.
You can have sectionGroup too. Example:
<configuration>
<configSections>
<sectionGroup name="x">
<section name="y" type="a, b"/>
</sectionGroup>
<configSections>
</configuration>

This class works as a general custom configuration section handler for any type...
public class XmlConfigurator : IConfigurationSectionHandler
{
public object Create(object parent, object configContext, XmlNode section)
{
if (section == null) return null;
Type sectionType = Type.GetType((string)(section.CreateNavigator()).Evaluate("string(#configType)"));
XmlSerializer xs = new XmlSerializer(sectionType);
return xs.Deserialize(new XmlNodeReader(section));
}
}
In your app.config, add
<section name="NameofConfigSection" type="NameSpace.XmlConfigurator, NameSpace.Assembly"/>
And in the configuration section element, add an attribute to specify the type you want the root element deserialized into..
<?xml version="1.0" encoding="utf-8" ?>
<NameofConfigSection configType="NameSpace.NameofTypeToDeserializeInto, Namespace.Assembly" >
...
</NameofConfigSection>