Question

您好我有药房购买表格，但打印/确认按钮有错误。打印时发生错误。我刚刚在网上找到了这个代码，我想用它。

这是我在pdf打印时遇到的错误。

错误来自float cash = float.Parse(txBCash.Text.Substring(1, 3));

这是代码

private void btnConfirm_Click(object sender, EventArgs e)
    {
        PrintDialog printDialog = new PrintDialog();

        PrintDocument printDocument = new PrintDocument();

        printDialog.Document = printDocument; //add the document to the dialog box...        

        printDocument.PrintPage += new System.Drawing.Printing.PrintPageEventHandler(CreateReceipt); //add an event handler that will do the printing

        //on a till you will not want to ask the user where to print but this is fine for the test envoironment.

        DialogResult result = printDialog.ShowDialog();

        if (result == DialogResult.OK)
        {
            printDocument.Print();

        }
    }
    public void CreateReceipt(object sender, System.Drawing.Printing.PrintPageEventArgs e)
    {

        int total = 0;
        float cash = float.Parse(txBCash.Text.Substring(1, 3));
        float change = 0.00f;

        //this prints the reciept

        Graphics graphic = e.Graphics;

        Font font = new Font("Courier New", 12); //must use a mono spaced font as the spaces need to line up

        float fontHeight = font.GetHeight();

        int startX = 10;
        int startY = 10;
        int offset = 40;

        graphic.DrawString(" Kwem Drugstore", new Font("Courier New", 18), new SolidBrush(Color.Black), startX, startY);
        string top = "Item Name".PadRight(30) + "Price";
        graphic.DrawString(top, font, new SolidBrush(Color.Black), startX, startY + offset);
        offset = offset + (int)fontHeight; //make the spacing consistent
        graphic.DrawString("----------------------------------", font, new SolidBrush(Color.Black), startX, startY + offset);
        offset = offset + (int)fontHeight + 5; //make the spacing consistent

        float totalprice = 0.00f;

        foreach (string item in listViewOrders.Items)
        {
            //create the string to print on the reciept
            string productDescription = item;
            string productTotal = item.Substring(item.Length - 6, 6);
            float productPrice = float.Parse(item.Substring(item.Length - 5, 5));

            //MessageBox.Show(item.Substring(item.Length - 5, 5) + "PROD TOTAL: " + productTotal);

        }

        change = (cash - totalprice);

        //when we have drawn all of the items add the total

        offset = offset + 20; //make some room so that the total stands out.

        graphic.DrawString("Total to pay ".PadRight(30) + String.Format("{0:c}", totalprice), new Font("Courier New", 12, FontStyle.Bold), new SolidBrush(Color.Black), startX, startY + offset);

        offset = offset + 30; //make some room so that the total stands out.
        graphic.DrawString("CASH ".PadRight(30) + String.Format("{0:c}", cash), font, new SolidBrush(Color.Black), startX, startY + offset);
        offset = offset + 15;
        graphic.DrawString("CHANGE ".PadRight(30) + String.Format("{0:c}", change), font, new SolidBrush(Color.Black), startX, startY + offset);
        offset = offset + 30; //make some room so that the total stands out.
        graphic.DrawString("     Thank-you for your purchase,", font, new SolidBrush(Color.Black), startX, startY + offset);
        offset = offset + 15;
        graphic.DrawString("       please come back soon!", font, new SolidBrush(Color.Black), startX, startY + offset);

    }
}

我不知道这是否正确或我是否正确地做到了。但请帮助我解决这个问题，因为我们学校的项目。

非常感谢任何类型的回复。提前谢谢。

Answer 1

C＃中的数组索引从零开始，而不是1.并且Substring方法的第二个参数不是结束位置，而是要检索的字符长度。因此，您的代码会从输入的第二个字符开始，从txBCash文本框中请求3个字符。如果你想获得前三个字符，那么你应该写

float cash = float.Parse(txBCash.Text.Substring(0, 3));

但更好的方法是通过float.TryParse，当输入不是有效的float时不会触发异常。当然你不能确定你的用户在那个文本框中只输入3个字符，所以我也会删除起始和长度限制

float cash = 0.0;
if(!float.TryParse(txBCash.Text, out cash))
   MessageBox.Show("Invalid value for cash");

从列表视图中打印收据

1 个答案: