我会做这样的：

• 使用一个 SqlConnectionStringBuilder 组件
• 定义之类的服务器名，从数据库名称等您的app.config
• 在该组件还具有两个属性的用户名和密码 - 填补这些从一个对话框，您提示用户输入这些信息
• 在该SqlConnectionStringBuilder然后给你正确的连接字符串用于连接到SQL服务器

• use a SqlConnectionStringBuilder component
• define things like server name, database name etc. from your app.config
• that component also has two properties for user name and password - fill those from a dialog box where you prompt the user for this information
• that SqlConnectionStringBuilder then gives you the proper connection string to use for connecting to your SQL Server

更新：

我的建议是将存储这样的基本的连接字符串：

My suggestion would be to store the basic connection string like this:

<configuration>
  <connectionStrings>
     <add name="MyConnStr" 
          connectionString="server=A9;database=MyDB;" />
  </connectionStrings>
</configuration>

然后装入这个骨架连接字符串 - 到你的 SqlConnectionStringBuilder （这是不完整的，仅是行不通的！）：

Then load this "skeleton" connection string (which is incomplete - that alone won't work!) into your SqlConnectionStringBuilder:

string myConnStr = ConfigurationManager.ConnectionStrings["MyConnStr"].ConnectionString;

SqlConnectionStringBuilder sqlcsb = new SqlConnectionStringBuilder(myConnStr);

然后抓住从用户的用户名和密码的对话框，然后将那些连接字符串生成器：

Then grab the user name and password from the user in a dialog box and add those to the connection string builder:

sqlcsb.UserID = tbxUserName.Text.Trim();
sqlcsb.Password = tbxPassword.Text.Trim();

，然后得到所产生的，完整的连接字符串中的 SqlConnectionStringBuilder ：

string completeConnStr = sqlcsb.ConnectionString;

using(SqlConnection _con = new SqlConnection(completeConnStr))
{
   // do whatever you need to do here....
}