c# - ConfigurationManager return null instead of string values

Question

I am trying to retrieve values from my App.config file which is stored in my working directory, however when I run the program it returns null. I am very confused why this is so, and have looked over the code many times in an attempt to spot an error.

Here is my App.config file code:

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
  <appSettings>
    <add key="provider" value="System.Data.SqlClient" />
  </appSettings>
  <connectionStrings>
    <add name="connection" connectionString="Data Source=(local)\SQLEXPRESS;Initial Catalog=Autos;Integrated Security=True;Pooling=False" />
  </connectionStrings>
</configuration>

Here is my C# code:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Configuration;
using System.Data;
using System.Data.Common;

namespace DataProviderFun
{
  class Program
  {
    static void Main(string[] args)
    {
      string p = ConfigurationManager.AppSettings["provider"];
      string c = ConfigurationManager.ConnectionStrings["connection"].ConnectionString;

      ...

When I run this code, p = null and c = null.

I have referenced System.Configuration.dll.

score 24 · Accepted Answer

Did you ensure that the config file is placed correctly at the directory from which you're running the application? Is there actually a file called <app name>.exe.config in that directory?

I'm just guessing here - maybe you added the App.Config file in a different project then your exe assembly project...?

By the way, I copied your code and App.Config as is to a clean project, and this code worked for me. So I'd look in the direction of the config file itself and not in the code. The code is fine...

Hope this helps,

Ran

score 1 · Accepted Answer

If your config file use in different class library you must change your name YourClasslibraryDllname.dll.config and you must change config file copy to output directory property

Ex:
   YourSolution
       ClassLibrary_1
            ClassLibrary_1.dll.config
            ApplicationConfigurationReader.cs
            ConfigurationConst.cs
       ClassLibrary_2
       ConsoleApp

Rename your config file like this YourClasslibraryDllname.dll.config
Open Properties Window
Change Do Not Copy to Copy Always

Add reference -> Assembly -> System.Configuration
Add below clases in ClassLibrary_1 Project

ConfigurationConst Class using System.Configuration;

public static class ConfigurationConst
{
   public static KeyValueConfigurationCollection Configs;
}

ApplicationConfigurationReader class using System.Configuration;

internal class ApplicationConfigurationReader
    {
        public void Read()
        {
            // read assembly
            var ExecAppPath = this.GetType().Assembly.Location;

            // Get all app settings  in config file
            ConfigurationConst.Configs = ConfigurationManager.OpenExeConfiguration(ExecAppPath).AppSettings.Settings;

        }
    }

Read Config using ClassLibrary_1;

static void Main(string[] args)
{
    new ApplicationConfigurationReader().Read();
    var Configval = ConfigurationConst.Configs["provider"].Value;            
    Console.ReadKey();
}

i Hope you can get clean help

score 0 · Accepted Answer

In Case all the settings are correct but still if you get null values, Please check your app.config file and replace the xml code as below,

<?xml version="1.0" encoding="utf-8"?>
<configuration>
  <appSettings>
    <add key="ClientSettingsProvider.ServiceUri" value="" />
  </appSettings>
</configuration>

Now Run your Code, you might see the proper values

score 0 · Accepted Answer

If you have .dll in your debug folder, then rename your confif file to yourprojectname.dll.config. This worked in my case

c# - ConfigurationManager return null instead of string values

4 回答 4

Related

Reference