How to check if an appSettings key exists?

user_86263 0
Viewed 155834

How do I check to see if an Application Setting is available?

i.e. app.config

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
  <appSettings>
    <add key ="someKey" value="someValue"/>
  </appSettings>
</configuration>

and in the codefile

if (ConfigurationManager.AppSettings.ContainsKey("someKey"))
{
  // Do Something
}else{
  // Do Something Else
}
configurationmanager appsettings c#
9 Answers

Upper options gives flexible to all manner, if you know key type try parsing them bool.TryParse(ConfigurationManager.AppSettings["myKey"], out myvariable);

user_12673770

I liked codebender's answer, but needed it to work in C++/CLI. This is what I ended up with. There's no LINQ usage, but works.

generic <typename T> T MyClass::ReadAppSetting(String^ searchKey, T defaultValue) {
  for each (String^ setting in ConfigurationManager::AppSettings->AllKeys) {
    if (setting->Equals(searchKey)) { //  if the key is in the app.config
      try {                           // see if it can be converted
        auto converter = TypeDescriptor::GetConverter((Type^)(T::typeid)); 
        if (converter != nullptr) { return (T)converter->ConvertFromString(ConfigurationManager::AppSettings[searchKey]); }
      } catch (Exception^ ex) {} // nothing to do
    }
  }
  return defaultValue;
}
user_92064830

Using the new c# syntax with TryParse worked well for me:

  // TimeOut
  if (int.TryParse(ConfigurationManager.AppSettings["timeOut"], out int timeOut))
  {
     this.timeOut = timeOut;
  }
user_123006330
Related