c# - 类中的 StreamReader 为空

Question

我有这个在类中创建 SqlConnection 字符串的方法。我从 .txt 文件中读取了数据，但问题是如果没有插入数据，应用程序甚至不会打开。我想知道如何在消息框中抛出异常并将该命令直接插入此类方法中。我不确定这是否可能。抱歉，如果我的回答过于琐碎或毫无意义。我很长时间没有编程了。

internal static class DataSource
    {
        private static string _ConnectionString;
        public static string ConnectionString
        {
            get
            {
                if (_ConnectionString == null)
                    _ConnectionString = FunctionToDynamicallyCreateConnectionstring();
                return _ConnectionString;
            }
        }
 private static string FunctionToDynamicallyCreateConnectionstring()
        {

                string path = "C:\\Users\\marek\\Documents\\Visual Studio 2012\\Projects\\tours\\tours\\sql_string.txt";
                StreamReader sr = new StreamReader(File.Open(path, FileMode.Open));

                SqlConnectionStringBuilder cb = new SqlConnectionStringBuilder();

                cb.DataSource = sr.ReadLine();
                cb.InitialCatalog = sr.ReadLine();
                cb.UserID = sr.ReadLine();
                cb.Password = sr.ReadLine();
                return cb.ToString();

        }

Answer 1

当您的应用通过 try/catch 启动时，包装对 DataSource.ConnectionString 的访问。下面是一些伪代码:

public void OnAppStart()
{
    string connString = null;
    try
    {
        connString = DataSource.ConnectionString;
    }
    catch (IOException ioe) 
    {
        MessageBox.Show("Hey, the file doesn't exist!");
    }
    catch (ArgumentNullException ane)
    {
        MessageBox.Show("Hey, the file is missing information!");
    }
    //You should be prepared to deal with a null or malformed connString 
    //from this point forwards
}