How to Fix NullReferenceException When Accessing Connection Strings from App.config?

Retrieving Connection Strings from App.config: Troubleshooting NullReferenceExceptions

Accessing connection strings from your App.config file using ConfigurationManager.ConnectionStrings["Test"] can sometimes throw a NullReferenceException. This guide provides solutions to this common problem.

Solutions:

1. Explicit Connection String Access:

   Instead of using ConfigurationManager.ConnectionStrings["Test"], directly access the ConnectionString property like this:

   <code class="language-csharp">System.Configuration.ConfigurationManager.ConnectionStrings["Test"].ConnectionString;</code>

2. Verify Assembly Reference:

   Make sure your project includes a reference to System.Configuration.dll. This assembly provides the necessary classes for accessing configuration settings.

App.config Example:

Here's a sample App.config file demonstrating the correct structure:

<code class="language-xml"><?xml version="1.0" encoding="utf-8"?>
<configuration>
  <connectionStrings>
    <add connectionString="Data Source=.;Initial Catalog=OmidPayamak;Integrated Security=True" 
         name="Test" 
         providerName="System.Data.SqlClient" />
  </connectionStrings>
</configuration></code>

Corrected Code Snippet:

This code snippet shows how to correctly retrieve the connection string:

<code class="language-csharp">string connectionString = System.Configuration.ConfigurationManager.ConnectionStrings["Test"].ConnectionString;</code>

Implementing these steps ensures successful retrieval of your connection string from App.config, enabling seamless database connectivity.

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