条形码输入后自动清除文本框并将值传递给文本文件

Question

这是我第一次使用此条形码扫描仪硬件。扫描完成后，该值将存储到textfile（记事本）中。我在输入条形码后自动清除文本框时遇到问题。我必须点击文本框再进行扫描。

public partial class Attendance : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {

    }

    protected void btnSave_Click(object sender, EventArgs e)
    {
        string Filename = "C:/Users/Nor  Asyraf  Mohd No/Documents/TestFile.txt";
        if (!File.Exists(Filename))
        {
            StreamWriter txtFile = File.CreateText(Filename);
            txtFile.Close();
            txtFile = File.AppendText(Filename);
            txtFile.WriteLine(txtText.Text);
            txtFile.Close();
        }
        else
            File.AppendAllText(Filename, txtText.Text + Environment.NewLine);
        txtText.Text = " ";
        lblError.Text = "Employee ID is saved";
        Response.AddHeader("REFRESH", "2;URL=Attendance.aspx");

    }


    protected void Button1_Click1(object sender, EventArgs e)
    {
        Response.Redirect("Default.aspx");
    }
}