Question

I’m slowly learning C# and bit confused about the code. I have here a simplified version of my class for the database connection settings

public class DatabaseSettings
{
    private static string connectionString = string.Empty;

    public static string ConnectionString
    {
        get 
        {
            return connectionString;
        }
        private set
        {
            connectionString = value;
        }
    }

    public bool TestConnection()
    {
        bool _returnVal = false;
        string _connectionString = String.Format("Data Source={0};Persist Security Info=False", databaseLocation);

        using (SqlCeConnection connection = new SqlCeConnection(_connectionString))
        {
            try
            {
                connection.Open();
                connectionString = _connectionString; // sets the value of the connection string here
                _returnVal = true;
            }
            catch (SqlCeException e)
            {
                // other codes here
                _returnVal = false;
            }
            finally
            {
                connection.Close();
            }
        }
        return _returnVal;
    }

    // other methods here
}

now on my Main Class, I am confused what is happening here. When i tried this code:

string _databaseLocation = "database path";
DatabaseSettings _dbaseSetting = new DatabaseSettings(_databaseLocation, true);
_dbaseSetting.TestConnection();
string newConnectionString = _dbaseSetting.ConnectionString;
//                                        ^ i got an error here
// Member 'SQLCE_Sample.ClassList.DatabaseSettings.ConnectionString.get' 
// cannot be accessed with an instance reference; 
// qualify it with a type name instead  

this one below works without an error but the problem is I got an empty string:

string _databaseLocation = "database path";
DatabaseSettings _dbaseSetting = new DatabaseSettings(_databaseLocation, true);
string newConnectionString = DatabaseSettings.ConnectionString;

What I really want is I need to create a class that has a public method which tests the connection from the application to the database. Inside that method contains a syntax that sets the value of the connection string. Then I need also a property that retrieves the value of the connection string without instantiating the class (that’s why i added the static keyword). How can I possibly to this?

Answer 1

It appears you want to access (statically) the value of a property that is set by an instance of your class. So, all you need to do is listen to the compiler error — access the property as a static reference rather than an instance reference. Change:

string newConnectionString = _dbaseSetting.ConnectionString;

To:

string newConnectionString = DatabaseSettings.ConnectionString;

You’ll of course need to make sure that you call TestConnection on the instance before you ever try to access the propery statically like this; otherwise ConnectionString will be null.