检查SQL连接是打开还是关闭

您如何检查我使用的是打开还是关闭的

 if (SQLOperator.SQLCONNECTION.State.Equals("Open"))

但是，即使状态为“打开”，它也无法通过此检查。

您应该使用SqlConnection.State

例如，

using System.Data;

if (myConnection != null && myConnection.State == ConnectionState.Closed)
{
   // do something
   // ...
}

这是我正在使用的：

if (mySQLConnection.State != ConnectionState.Open)
{
    mySQLConnection.Close();
    mySQLConnection.Open();
}

我不简单使用的原因：

if (mySQLConnection.State == ConnectionState.Closed)
{
    mySQLConnection.Open();
}

是因为ConnectionState也可以是：

Broken, Connnecting, Executing, Fetching

此外

Open, Closed

此外，Microsoft声明关闭并重新打开连接“将刷新State的值”。参见此处http://msdn.microsoft.com/zh-cn/library/system.data.sqlclient.sqlconnection.state(v=vs.110).aspx

.NET文档说：状态属性：ConnectionState值的按位组合

所以我认为你应该检查

!myConnection.State.HasFlag(ConnectionState.Open)

代替

myConnection.State != ConnectionState.Open

因为State可以有多个标志。

检查MySQL连接是否打开

ConnectionState state = connection.State;
if (state == ConnectionState.Open)
{
    return true;
}
else
{
    connection.Open();
    return true;
}

你也可以用这个

if (SQLCON.State == ConnectionState.Closed)
{
     SQLCON.Open();
}

这段代码更具防御性，在打开连接之前，请检查状态。如果连接状态为“断开”，则应尝试将其关闭。断开意味着该连接先前已打开并且无法正常运行。第二个条件确定必须再次关闭连接状态才能尝试再次打开它，以便可以重复调用该代码。

// Defensive database opening logic.

if (_databaseConnection.State == ConnectionState.Broken) {
    _databaseConnection.Close();
}

if (_databaseConnection.State == ConnectionState.Closed) {
    _databaseConnection.Open();
}

要检查数据库连接状态，您可以简单地执行以下操作

if(con.State == ConnectionState.Open){}

要检查OleDbConnection状态，请使用以下命令：

if (oconn.State == ConnectionState.Open)
{
    oconn.Close();
}

State 返回 ConnectionState

public override ConnectionState State { get; }

这是另一个ConnectionState枚举

public enum ConnectionState
    {
        //
        // Summary:
        //     The connection is closed.
        Closed = 0,
        //
        // Summary:
        //     The connection is open.
        Open = 1,
        //
        // Summary:
        //     The connection object is connecting to the data source. (This value is reserved
        //     for future versions of the product.)
        Connecting = 2,
        //
        // Summary:
        //     The connection object is executing a command. (This value is reserved for future
        //     versions of the product.)
        Executing = 4,
        //
        // Summary:
        //     The connection object is retrieving data. (This value is reserved for future
        //     versions of the product.)
        Fetching = 8,
        //
        // Summary:
        //     The connection to the data source is broken. This can occur only after the connection
        //     has been opened. A connection in this state may be closed and then re-opened.
        //     (This value is reserved for future versions of the product.)
        Broken = 16
    }

我使用以下方式 sqlconnection.state

if(conexion.state != connectionState.open())
   conexion.open();