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无法将 OdbcConnection 设置为 OdbcCommand.Connection

发布于 2024-08-09 17:25:07 字数 383 浏览 2 评论 0原文

在类级别，我创建了引用：

System::Data::Odbc::OdbcConnection Connection;

在某种方法中，我想将其设置为 odbcCommand.Connection，如下所示：

::System::Data::Odbc::OdbcCommand Command; Command.Connection=this->连接；

它报告“无法将参数 1 从 'System::Data::Odbc::OdbcConnection' 转换为 'System::Data::Common::DbConnection ^'”

我不明白为什么它谈到 common::DbConnection 如果命令。连接需要 OdBcConnection？谢谢

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终难愈 2024-08-16 17:25:07

Command.Connection 想要 System::Data::Common::DbConnection 的句柄 (^)

public:
property OdbcConnection^ Connection {
    OdbcConnection^ get ();
    void set (OdbcConnection^ value);
}

相反，请尝试执行此操作：

System::Data::Odbc::OdbcCommand Command; 
Command.Connection = %Connection;

一元 % 运算符 (跟踪引用) 返回对 CLI 对象的 CLI 跟踪引用。跟踪引用对句柄和值类型有效。

对评论的回应：

当您以这种方式创建托管对象时：

OdbcConnection Connection;

它是一种特殊类型的 C++/CLI 对象，在堆栈上分配并指向托管堆上的托管对象。它不是有效的托管引用对象。要创建托管引用，您需要执行以下操作。

OdbcConnection^ Connection; // In the class definition 

// In the class constructor do the following: 
Connection = gcnew OdbcConnection();

并且应在构造函数中删除DB连接以保证及时清理。但管理对象不需要，它们会自动删除

Command.Connection wants a handle (^) to a System::Data::Common::DbConnection

public:
property OdbcConnection^ Connection {
    OdbcConnection^ get ();
    void set (OdbcConnection^ value);
}

Instead try to do this:

System::Data::Odbc::OdbcCommand Command; 
Command.Connection = %Connection;

The unary % operator (Tracking reference) returns a CLI tracking references to a CLI object. Tracking references are valid to handles and value types.

Response to comment:

When you create a managed object this way:

OdbcConnection Connection;

It's a special type of C++/CLI object that are allocated on the stack and that points to the managed object on the managed heap. It isn't a valid managed reference object. To create a managed reference you need to do the following.

OdbcConnection^ Connection; // In the class definition 

// In the class constructor do the following: 
Connection = gcnew OdbcConnection();

And DB connection should be deleted in the constructor to guarantee timely clean up. But it is not needed for managed object, they are delete automatically

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