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Why is System.Data.SqlClient.SqlConnection class throwing an exception that "The parameter is incorrect"?

I'm attempting to learn how to set up database connections using a local SQL database and an ASP.NET MVC project, using .NET framework 4.5.

Here are the steps I've taken that lead up to this:

  1. Created a new SQL Server database in my project App_Data folder, called TestSQLdb.mdf.

  2. Created a connection string in web.config: 

    <add name="SQLTestConnection1" 
     connectionString="Data Source=(LocalDB);initial catalog=TestSQLdb;Integrated Security=true" />

  3. Access the connection string through 

    string cn_str = ConfigurationManager.ConnectionStrings["SQLTestConnection1"].ConnectionString;

    (See this SO thread for more info on this).

  4. Created a new connection: 

    SqlConnection conn = new SqlConnection(cn_str);

  5. Attempt to open the connection: 

    try
{
     conn.Open();

    At this point, an exception is thrown.

I tried to set this up so it would be simple and easy to learn on. What am I missing?

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Aaron Thomas
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  • Do you really call a method `cn_str()` in your `new SqlConnection` or is it just a typo? – Pilgerstorfer Franz Feb 23 '15 at 20:50
  • @PilgerstorferFranz: the `cn_str()` method is correct in my code, but for example here it should just be `cn_str`. Thanks for pointing it out. I'll edit my question, since this was also pointed out by @NightOwl888 in his answer below. – Aaron Thomas Feb 23 '15 at 21:06

2 Answers2

9

When you are working with a localDB you'll have to specify a AttachDbFileName attribute in your connectionString. This attribute should point to your TestSQLdb.mdf file. Initial catalog is the name of your dataBase within your mdf file.

see MSDN for this example

<add name="ConnectionStringName"
providerName="System.Data.SqlClient"
connectionString="Data Source=(LocalDB)\v11.0;AttachDbFileName=|DataDirectory|\DatabaseFileName.mdf;InitialCatalog=DatabaseName;Integrated Security=True;MultipleActiveResultSets=True" />
Pilgerstorfer Franz
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0

You are not passing a variable to the new SqlConnection, you are instead trying to call a function called cn_str.

To get it to work, you need to remove the parentheses from the name.

SqlConnection conn = new SqlConnection(cn_str);
NightOwl888
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  • Umm, my fault I didn't point out that I'm actually using a function to get `cn_str`. Thanks for pointing that out, but it's not actually the problem here I think. I'll edit my question if needed. – Aaron Thomas Feb 23 '15 at 21:05
  • If this had been the problem, the error message would have been different and the exception would have happened at a different time. – mason Feb 23 '15 at 21:25