Question

这是我的头脑。我已尝试try和catch finally和其他事情，但这个错误不断回来。请一些帮助。我的c＃代码：

 void show()
    {
       string str = "SELECT PID, Pname, Gender, ContactNum, Category, Department, Ward, AdmitDate, DischargeDate, NumOfDays, CostOfTest, NumOfDocsVisited, DocFee, BedCost, TotalCost, GrandTotal FROM Patient";
        cmd = new SqlCommand(str, con);
            con.Open();
            SqlDataAdapter adp = new SqlDataAdapter(cmd);
            DataTable dt = new DataTable();
            adp.Fill(dt);
            GridView1.DataBind();
                con.Close();
    }

错误是：

连接未关闭。连接的当前状态是打开的。描述：执行期间发生未处理的异常当前的网络请求。请查看堆栈跟踪了解更多信息有关错误的信息以及它在代码中的起源异常详细信息：System.InvalidOperationException：连接没有关闭。连接的当前状态是打开的。

来源错误：

Line 50:            string str = "SELECT PID, Pname, Gender, ContactNum, Category, Department, Ward, AdmitDate, DischargeDate, NumOfDays, CostOfTest, NumOfDocsVisited, DocFee, BedCost, TotalCost, GrandTotal FROM Patient";
Line 51:             cmd = new SqlCommand(str, con);
Line 52:                 con.Open();
Line 53:                 SqlDataAdapter adp = new SqlDataAdapter(cmd);
Line 54:                 DataTable dt = new DataTable();

堆栈追踪：

[InvalidOperationException: The connection was not closed. The connection's current state is open.]
System.Data.ProviderBase.DbConnectionInternal.TryOpenConnection(DbConnection outerConnection, DbConnectionFactory connectionFactory, TaskCompletionSource`1 retry, DbConnectionOptions userOptions) +14
System.Data.SqlClient.SqlConnection.TryOpenInner(TaskCompletionSource`1 retry) +94
System.Data.SqlClient.SqlConnection.TryOpen(TaskCompletionSource`1 retry) +110
System.Data.SqlClient.SqlConnection.Open() +96
SMC.Billing.show() in e:\VS2013 projects\SMC\SMC\Billing.aspx.cs:52
SMC.Billing.Button3_Click(Object sender, EventArgs e) in e:\VS2013 projects\SMC\SMC\Billing.aspx.cs:97
System.Web.UI.WebControls.Button.OnClick(EventArgs e) +9628722
System.Web.UI.WebControls.Button.RaisePostBackEvent(String eventArgument) +103
System.Web.UI.WebControls.Button.System.Web.UI.IPostBackEventHandler.RaisePostBackEvent(String eventArgument) +10
System.Web.UI.Page.RaisePostBackEvent(IPostBackEventHandler sourceControl, String eventArgument) +13
System.Web.UI.Page.RaisePostBackEvent(NameValueCollection postData) +35
System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +1724

Answer 1

在我看来，它试图告诉您，您正在尝试打开已经打开的连接。

您可以尝试（第52行）

if (con.State == ConnectionState.Closed) con.Open;

Answer 2

将您的连接包裹在using块中。这保证了它总是被关闭。

using (var connection = new SqlConnection(connectionString))
{
  connection.Open();
  //Do stuff with the connection
}

连接未关闭

2 个答案: