Connection String Is Not Working Object Instance Reference Is Null

//'Object reference not set to an instance of an object.' Please Do not mark it as redundant question . I have tried almost all the methods to make a connection string first one

Solution 1:

There are many ways to connect to your SQL Server database within a C# app.

1. The First way, that is not recommended, is hard coding:

   publicvoidCreateMySqlConnection()
   {
       MySqlConnectionStringBuildermyCSB=newMySqlConnectionStringBuilder();
       myCSB.Port = 3307;
       myCSB.Host = "localhost";
       myCSB.UserId = "root";
       myCSB.Password = "mypassword";
       myCSB.Direct = true;
       myCSB.Compress = true;
       myCSB.Database = "demobase";
       myCSB.MaxPoolSize = 150;
       myCSB.ConnectionTimeout = 30;
       MySqlConnectionmyConnection=newMySqlConnection(myCSB.ConnectionString);
   }
   

from: https://www.devart.com/dotconnect/connection-strings.html?gclid=CjwKCAjwy_XaBRAWEiwApfjKHt-Yn6Ja43anKj0cvAzDHL5eNDHKvaxwnq5IEsVyHY-rR3GECsa6shoCZH8QAvD_BwE

2. The second way, anwsering the question being already anwsered by @sellotape at the author comments, is puting the connection string at you web.config:

   <add name="MovieDB"
        connectionString="Data Source=LocalDb)\MSSQLLocalDB;Initial Catalog=aspnet-MvcMovie;Integrated Security=SSPI;AttachDBFilename=|DataDirectory|\Movies.mdf"     
        providerName="System.Data.SqlClient"/>
   

to read it:

System.Configuration.ConfigurationrootWebConfig=
            System.Web.Configuration.WebConfigurationManager.OpenWebConfiguration("/MyWebSiteRoot");
        System.Configuration.ConnectionStringSettings connString;
        if (rootWebConfig.ConnectionStrings.ConnectionStrings.Count > 0)
        {
            connString =
                rootWebConfig.ConnectionStrings.ConnectionStrings["MovieDB"];
            if (connString != null)
                Console.WriteLine("MovieDB connection string = \"{0}\"",
                    connString.ConnectionString);
            else
                Console.WriteLine("No MovieDB connection string");
        }

The name at your web.config tag 'name'

    <add name="MovieDB".....

has to be the same one from your c# code:

connString = rootWebConfig.ConnectionStrings.ConnectionStrings["MovieDB"]

You don´t need to specify a large name as you did: "ClinicalDAO.Properties.Settings.ClinicalConnectionString"

Make it smaller and simple.

from: https://msdn.microsoft.com/en-us/library/ms178411.aspx

Don´t forget to secure your connection string at your web.config. Please, read this: https://msdn.microsoft.com/en-us/library/ms178372.aspx