如何判断一台机器是否连接了扫描仪，我使用“吐温" [英] how to judge one machine connect a scanner,I use the "twain"

问题描述

现在我还没有将清理器连接到我的机器上
我的代码-单击扫描按钮:

now I have not connect a sanner to my machine
my code --click the scan button:

private void btnScan_Click(object sender, EventArgs e)
        {
            if (!msgfilter)
            {
                this.Enabled = false;
                msgfilter = true;
                Application.AddMessageFilter(this);
            }
            //i want judge if one scanner is connected first,if no ,then do noting……
            tw.Acquire();
            this.txtTotalPages.Enabled = false;
        }
// then do loop next fun--
bool IMessageFilter.PreFilterMessage(ref Message m)
        {
            //
            TwainCommand cmd = tw.PassMessage(ref m);
            if (cmd == TwainCommand.Not)
                return false;
            switch (cmd)
            {
                case TwainCommand.CloseRequest:
                    {
                        EndingScan();
                        tw.CloseSrc();
                        break;
                    }
                case TwainCommand.CloseOk:
                    {
                        EndingScan();
                        tw.CloseSrc();
                        break;
                    }
                case TwainCommand.DeviceEvent:
                    {
                        break;
                    }
                case TwainCommand.TransferReady:
                    {

推荐答案

非常感谢，我在跟踪代码时发现了麻烦，当我没有连接一台扫描仪时，我单击了sanner按钮，它将循环执行功能----

Thanks very much,I have found the trouble when I track the code,when I did not connect one scanner,I click the sanner button ,it will do loop the funntion----

bool IMessageFilter.PreFilterMessage(ref Message m) ...

为什么循环，我跟踪我的代码并发现它执行了代码://

why do loop that,I track my code and found it perform the code： //

TwainCommand cmd = tw.PassMessage(ref m);
if (cmd == TwainCommand.Not)
    return false;

现在我将其更改如下:

now I changed it like below:

if (cmd == TwainCommand.Not)
            {
                EndingScan();
                tw.CloseSrc();
                return false;
            }

现在可以了，这是我的错，我太粗心了……
再次感谢…………

now it is ok,it is my fault,I am so careless……
thank s again……

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