Check if SQL Connection is Open or Closed

问题

How do you check if it is open or closed I was using

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

however, even the State is 'Open' it fails on this check.

回答1:

You should be using SqlConnection.State

e.g,

using System.Data;

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

回答2:

Here is what I'm using:

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

The reason I'm not simply using:

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

Is because the ConnectionState can also be:

Broken, Connnecting, Executing, Fetching

In addition to

Open, Closed

Additionally Microsoft states that Closing, and then Re-opening the connection "will refresh the value of State." See here http://msdn.microsoft.com/en-us/library/system.data.sqlclient.sqlconnection.state(v=vs.110).aspx

回答3:

The .NET documentation says: State Property: A bitwise combination of the ConnectionState values

So I think you should check

!myConnection.State.HasFlag(ConnectionState.Open)

instead of

myConnection.State != ConnectionState.Open

because State can have multiple flags.

回答4:

Check if a MySQL connection is open

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

回答5:

you can also use this

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

回答6:

This code is a little more defensive, before opening a connection, check state. If connection state is Broken then we should try to close it. Broken means that the connection was previously opened and not functioning correctly. The second condition determines that connection state must be closed before attempting to open it again so the code can be called repeatedly.

// Defensive database opening logic.

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

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

回答7:

To check the database connection state you can just simple do the following

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

回答8:

To check OleDbConnection State use this:

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

State return the ConnectionState

public override ConnectionState State { get; }

Here are the other ConnectionState enum

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
    }

回答9:

I use the following manner sqlconnection.state

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

来源：https://stackoverflow.com/questions/6943933/check-if-sql-connection-is-open-or-closed

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sqlconnection