While trying to connect to SQLServer from C# the error # reported is 4060 and I get...

System.Data.SqlClient.SqlException HResult=0x80131904
Message=Cannot open database "MyDatabase" requested by the login. The login failed. Login failed for user 'DBClient'.
Source=.Net SqlClient Data Provider StackTrace:

When using the credentials from SSMS, all is good.

1. Using SQL authentication.
2. The MSSQL database server is a different machine on the local network.
3. The C# code is on a dev machine and the error occurs when clicking the "IIS Express Google Chrome" button to view in a browser. Here is the C# code...

sqlConnect = new SqlConnection();

sqlConnect.ConnectionString = "Data Source = SlaDAS; Initial Catalog = MyDatabase; Uid = DBClient; Pwd = 123456PW; Connection Timeout = 30; Max Pool Size = 500";

sqlConnect.Open();

I have also tried a lot of different versions of the string and everything returns this error.

Thanks for all help, Stanley

We can get Visual Studio to help you generate a working connection string:

• Add a new DataSet type object to your project
• Open it, right click anywhere and choose Add TableAdapter
• Go through the wizard, at some point you'll have to create a connection string. Click Add Connection:

• If the database type is wrong (mine has opened suggesting Access), click Change:

• Change it to SQL Server, and check it uses the SQLS driver, not the OLE one:

• You might see this, click OK if you do:

• And then fill in the rest of your details, the dialog should look mostly like SSMS; fill in the same details, click Test Connection or tweak some things etc til you get success..

• On the next page of the wizard, choose "SQL that retrieves rows", fill in some query, SELECT * FROM Person WHERE id = @id - it doesn't matter what table, especially if you aren't going to use this strongly typed dataset as your data access layer.. Just make it any valid query as a test
• Name it FillById
• Finish the wizard

Now your settings file of your app contains a working connection string

You could use it from there, copy it etc if you're using EF, dapper or some other ORM, and throw the DataSet away but if you're planning on using data adapters and datatables like this:

using(var da as new DataAdapter("SELECT * FROM Person WHERE ID = @x", "Data Source=...."){
  da.SelectCommand.Parameters.AddWithValue("@x", 1234);
  var dt = new DataTable();
  da.Fill(dt);
  
  int age = Convert.ToInt32(dt.Rows[0]["Age"]);
  ...

}

Honestly it's easier and better to just do a tableadapter like:

var ta = new PersonTableAdapter(); //it's like a data adapter
var dt = new PersonDataTable();    //it's a datatable with extra properties so no casting

ta.FillById(dt, 1234);             //load record with id 1234

int age = dt[0].Age;               //it's an int already, no convert etc like above

You can add more queries to the tableadapter by right clicking it and choosing Add Query, e.g. so you can add SELECT * FROM Person WHERE FirstName LIKE @firstname and call it FillByFirstNameLike then:

ta.FillByFirstNameLike(dt, "Jo%"); //find all person names starting with Jo

Or to return a datatable:

var dt = ta.GetDataByFirstNameLike("Jo%"); //get a new PersonDataTable 

TLDR

Use Visual Studio to help you create a working connection string using the wizards in a DataSet. As part of the process you'll have to get a working connection and you'll be able to easily prove it working and test downloading data/connection etc without tedious trial and error doing it in code. When you're done the correct connection string is in your settings/config and can just be used from there directly. You can discard the dataset, but if you're planning on using dataadapters and datatables to retrieve your data, it'll make life a lot easier to use the tableadapters and strongly typed datatables in the dataset instead