Get connection string from App config

Question

var connection   ConnectionFactory GetConnection      ConfigurationManager ConnectionStrings  Test        ConnectionString  DataBaseProvider     And this is my App config     lt  xml version  1 0  encoding  utf-8    gt   lt configuration gt       lt connectionStrings gt           lt add name  Test  connectionString  Data Source   Initial Catalog OmidPayamak Integrated Security True  providerName  System Data SqlClient    gt       lt  connectionStrings gt   lt  configuration gt    But when my project runs this is my error      Object reference not set to an instance of an object

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Since this is very common question I have prepared some screen shots from Visual Studio to make it easy to follow in 4 simple steps

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Get Connection from web config file public static OdbcConnection getConnection         OdbcConnection con   new OdbcConnection        con ConnectionString   System Configuration ConfigurationManager ConnectionStrings  con   ConnectionString      return con

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This worked for me   string connection   System Configuration ConfigurationManager ConnectionStrings  Test   ConnectionString    Outputs      Data Source   Initial Catalog OmidPayamak IntegratedSecurity True

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First you have to add System Configuration reference to your project and then use below code to get connection string    connectionString   ConfigurationManager ConnectionStrings  MYSQLConnection   ConnectionString ToString

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Can t you just do the following    var connection        System Configuration ConfigurationManager      ConnectionStrings  Test   ConnectionString    Your assembly also needs a reference to System Configuration dll

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First Add a reference of System Configuration to your page   using System Configuration    Then According to your app config get the connection string as follow   string conStr   ConfigurationManager ConnectionStrings  Test   ToString      That s it now you have your connection string in your hand and you can use it

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You can use this method to get connection string  using System   using System Configuration   private string GetConnectionString         return ConfigurationManager ConnectionStrings  MyContext   ConnectionString

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I had the same Issue  my solution was built up from two projects  A Class library and a website referencing to the class library project  the problem was that i was trying to access the App config in my Class library project but the system was searching in Web config of the website  I put the connection string inside Web config and     problem solved   The main reason was that despite ConfigurationManager was used in another assembly it was searching inside the runnig project

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string sTemp   System Configuration ConfigurationManager ConnectionStrings  myDB In app config   ConnectionString

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1  Create a new form and add this   Imports System Configuration Imports Operaciones My MySettings  Public NotInheritable Class frmconexion      Private Shared  cnx As String     Public Shared Property ConexionMySQL   As String         Get             Return My MySettings Default conexionbd         End Get         Private Set ByVal value As String               cnx   value         End Set     End Property  End Class   then when you want to use the connection do this in ur form    Private Sub frmInsert Load ByVal sender As System Object  ByVal e As System EventArgs  Handles MyBase Load  Dim cn As New MySqlConnection frmconexion ConexionMySQL  cn open     and thats it  You will be connected to the DB and can do stuff    This is for vb net but the logic is the same

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You can fetch the connection string by using below line of code -  using System  using System Configuration   var connectionString ConfigurationManager ConnectionStrings  MyConnectionString   ConnectionString    Here is a reference    Connection String from App config

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Try this out   string abc   ConfigurationManager ConnectionStrings  CharityManagement   ConnectionString

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Also check that you ve included the System Configuration dll under your references  Without it  you won t have access to the ConfigurationManager class in the System Configuration namespace

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It is possible that the OP in this question is trying to use an App Config within a dll   In this case  the code is actually trying to access the App Config of the executable and not the dll   Since the name is not found  you get a Null returned  hence the exception shown   The following post may be helpful  ConnectionString from app config of a DLL is null

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Have you tried   var connection   new ConnectionFactory   GetConnection      ConfigurationManager ConnectionStrings  Test        ConnectionString  DataBaseProvider

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I solved the problem by using the index to read the string and checking one by one  Reading using the name still gives the same error  I have the problem when I develop a C  window application  I did not have the problem in my asp net application  There must be something in the setting which is not right

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It seems like problem is not with reference  you are getting connectionstring as null so please make sure you have added the value to the config file your running project meaning the main program library that gets started executed first

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I referenced System Configuration library and I have the same error  The debug files had not their app config  create manually this file  The error is  I solved this copying the file  appname exe config  in debug folder  The IDE was not create the file

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string str   Properties Settings Default myConnectionString

[c#] Get connection string from App.config

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