c# - "using"语句与大括号

我想知道为什么我们在C#中使用using语句。我查了一下，发现它用于执行语句，然后清理对象。所以我的问题是:如果我们打开和关闭大括号({ })来定义范围，那不是同一回事吗？

使用语句:

using (SqlConnection conn = new SqlConnection(connString)) {
     SqlCommand cmd = conn.CreateCommand();
     cmd.CommandText = "SELECT * FROM Customers";
     conn.Open();
     using (SqlDataReader dr = cmd.ExecuteReader()) {
          while (dr.Read())
          // Do Something...
     }
}

弯括号:

{
     SqlConnection conn = new SqlConnection(connString);
     SqlCommand cmd = conn.CreateCommand();
     cmd.CommandText = "SELECT * FROM Customers";
     conn.Open();
     {
          SqlDataReader dr = cmd.ExecuteReader();
          while (dr.Read())
          // Do Something...
     }
}

两种方法之间有什么显着差异吗？

最佳答案

好吧，使用(仅当该类实现IDisposable接口(interface)时才合法)

using (SqlConnection conn = new SqlConnection(connString)) {
  // Some Code
  ...
}

等于此代码块

SqlConnection conn = null;

try {
  SqlConnection conn = new SqlConnection(connString);

  // Some Code
  ...
}
finally {
  if (!Object.ReferenceEquals(null, conn))
    conn.Dispose();
}

C#与C++的行为不同，因此请勿像在C++中那样在C#中使用{...}模式:

{
  SqlConnection conn = new SqlConnection(connString);
  ...
  // Here at {...} block exit system's behavior is quite different:
  //
  // C++: conn destructor will be called,
  // resources (db connection) will be safely freed
  //
  // C#:  nothing will have happened!
  // Sometimes later on (if only!) GC (garbage collector)
  // will collect conn istance and free resources (db connection).
  // So, in case of C#, we have a resource leak
}

关于c# - "using"语句与大括号，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/18227852/