I have created a Windows Forms application and I am getting data from my database in it, but I have a problem: the SqlConnection object cannot be instantiated.
When I declare this connection string, it works:
static string connectionString = "Data Source=DEVELOPMENT-PC\\SQLEXPRESS;Initial Catalog=DATABASE;Integrated Security=True";
But when I retrieve this from textfile, it doesn't work:
static string a = File.ReadAllText(Path.Combine(Path.GetDirectoryName(Environment.GetCommandLineArgs()[0]), "connectionString.txt")).ToString();
One point: when I write MessageBox.Show(a);, I see in the window the same string as connection string shown above is.
What could be the problem?
The issue is actually that you have two slashes in the text file. The string is escaped in C# but does not need to be escaped in the text file. The C# is like this:
"Data Source=DEVELOPMENT-PC\\SQLEXPRESS;Initial Catalog=DATABASE;Integrated Security=True"
Where the text file should just have a single slash:
Data Source=DEVELOPMENT-PC\SQLEXPRESS;Initial Catalog=DATABASE;Integrated Security=True
This is because you are escaping the slashes in C#, the text file doesn't require escaping the string. For example a string like "This is my\nstring" in C# is two lines, if you want the same effect in a text file you just write it on two lines. The slash is the start of an escape sequence, by writing \ you are telling it to ignore it and use a single slash in its place.
If you only want a single slash in the C# code, you can do that too:
static string connectionString = @"Data Source=DEVELOPMENT-PC\SQLEXPRESS;Initial Catalog=DATABASE;Integrated Security=True";
Here the @ symbol tells the compiler that the following string does not contain any escape sequences and to treat it as a literal. This makes it easier especially when working with file paths so you don't have to escape all the slashes.