I am sure you are already using one tool or other ....but I always found UDL file as the easiest way to create a connection string.......
What is UDL file?
UDL is Universal Data Link file contains the connection information.
So how to create one....
Step 1: Right click in the folder you want to create a UDL file and select the option New and Select the option Text Document from the drop down menu.
Step 2: Open the text file and from the File menu select the option Save As
Step 3: Enter the file name as xyz.udl (choose any name you prefer but make sure the extension is .udl)
Step 4: Select the All Files option select in the Save As Type drop down below
Step 5: Click the Save button in the Save As dialog box
You can see that a new udl file is created with the name you chose. Now what....?
Double click the UDL file you just created...you will be provided with the Data Link Properties dialog box.
Set the properties according to your need... I mean the Provider, Data source, Login info and the database name..etc.
You can also test the connection to make sure the information you provided are correct.
Once the test is completed sucessfully click Ok to close the Data Link Properties dialog box.
Open the the UDL file in a text editor and your connection string is ready....