Differences in behavior between System.Web.Configu

I had some trouble on a test server with an ASP.NET website. I goofed, and had the home directory of the Default Web Site pointed to the wrong place. When I tried:

ConfigurationManager.ConnectionStrings["connectionString"];

it returned null, but

using System.Web.Configuration;

/* ... */

var rootWebConfig =
    WebConfigurationManager.OpenWebConfiguration(Request.ApplicationPath);

WebConfigurationManager.OpenWebConfiguration(Request.ApplicationPath);

rootWebConfig.ConnectionStrings.ConnectionStrings["connectionString"].ConnectionString;`

returned the correct connection string.

What are all the differences between the two approaches?

EDIT: What I'm really asking is, why does the ConfigurationManager approach fail when the home directory is incorrectly set, but succeeds otherwise, and the WebConfigurationManager succeeds regardless of whether the home directory is correctly set? Are there any other differences, such as assumptions about access control?

回答1:

Try This:

Put a breakpoint where your ConfigurationManager statement is and run the following in the Immediate Output window ((ConfigurationSection) ConfigurationManager.GetSection("connectionStrings")).ElementInformation . My machine reports Source: "C:\Users\John\Documents\Visual Studio 2008\Projects\StackOverflowCode\WebApplication1\web.config" as seen below.

Note: The following also shows mine is accessing the ASP.NET web.config.

{System.Configuration.ElementInformation}
    Errors: {System.Configuration.ConfigurationException[0]}
    IsCollection: true
    IsLocked: false
    IsPresent: true
    LineNumber: 17
    Properties: {System.Configuration.PropertyInformationCollection}
    Source: "C:\\Users\\John\\Documents\\Visual Studio 2008\\Projects\\StackOverflowCode\\WebApplication1\\web.config"
    Type: {Name = "ConnectionStringsSection" FullName = "System.Configuration.ConnectionStringsSection"}
    Validator: {System.Configuration.DefaultValidator}

And when I run ConfigurationManager.ConnectionStrings.ElementInformation I get Source:null which is correct for my web app.

What do you get for a configuration Source path???

Immediate Assumption

ConfigurationManager.ConnectionStrings["connectionString"]; might look for a config location which isn't necessarily the same as the web application's root web.config. Likely it's looking in a Windows directory (e.g at a different place or for machine.config). Trying to find an appropriate test for this though.

Intentions of Each Manager

System.Configuration.ConfigurationManager can access the .NET configuration XML format which means it reads both:

web configurations (i.e. web.config file in ASP.NET)
and non-web configurations (e.g. app.config file - standalone console app, Windows app, etc.)

and expresses those aspects that are common to types of configuration. This is a general purpose config manager. (However despite this ability to look at both types of configs, you should use it for app configs because the web manager is devoted to the web configs, as described next ...)

System.Web.Configuration.WebConfigurationManager does pretty much the same thing but is the "webified" version of configuration manager, providing access to ASP.NET web-specific aspects of configuration (e.g. web.config file in ASP.NET).

Similarities

See member similarities between ConfigurationManager.* and WebConfigurationManager.*

Both managers can, for example, access an AppSettings property and a ConnectionStrings property. Indeed both these settings are common to both kinds of config and are even located at the same level in the XML document.

So there are many similarities however,

Behavioral Differences

Accessing configuration: ConfigurationManager has methods to open standalone app configs (i.e. Myprogram.EXE's App.config) relative to the EXEC app, whereas WebConfigurationManager has methods to open the ASP.NET web config relative to it's web application root directory in the web site.

Here's a basic app.config (e.g. opened via "C:\winapp\app.config" from a disk folder by ConfigurationManager)

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
  <appSettings/>
  <connectionStrings/>
</configuration>

And here's a basic web.config (e.g. opened via "~" meaning root of web site by WebConfigurationManager)

<?xml version="1.0"?>
<configuration>  
    <appSettings/>
    <connectionStrings/>

    <system.web>
        <!-- special web settings -->
    </system.web>

</configuration>

Notice the similarities. Also notice the web configuration has an additional system.web element for ASP.NET.

These managers are located in different assemblies.