PrintDocument HasMorePages不工作

Question

我想打印数据网格中的数据。代码可以很好地处理第一页，但是注释行不能很好地工作，并且不会移动到下一页。有人能帮我解决这个问题吗？

private void DrawFactorA4(object sender, PrintPageEventArgs ev)
    {
     for (int j = 0; j < GrdRDocument.Rows.Count; j++)
        {
            i += 2;
            //draw data grid
            s++;
            if(s == 10)
            {    
               //ev.HasMorePages = true;  //this line doesn't work
               s = 0;
               i = 0;                 
            }
            else
            {
               ev.HasMorePages = false;                    
            }
        }
    }

_

private void BtnPrint_Click(object sender, EventArgs e)
    {
        printFont = new Font("Arial", 12);

        IEnumerable<PaperSize> paperSizes = 

        pd.PrinterSettings.PaperSizes.Cast<PaperSize>();

        sizeA4 = paperSizes.First<PaperSize>(size => size.Kind == PaperKind.A4);

        pd.DefaultPageSettings.Landscape = true;

        pd.DefaultPageSettings.PaperSize = sizeA4;

        pd.PrintPage += new PrintPageEventHandler(this.DrawFactorA4);

        printPreviewDialog.Document = pd;

        printPreviewDialog.ShowDialog();
    }

Answer 1

停下来读一读你所拥有的：

printFont = new Font("Arial", 12);

字体是非托管资源；在这里，您正在创建一个字体，并且永远不会将其丢弃。也许在这种特殊情况下这是无害的，但这是一个很难养成的坏习惯。

pd.PrintPage += new PrintPageEventHandler(this.DrawFactorA4);

文档中的每一页都将调用DrawFactorA4。DrawFactorA4内幕

for (int j = 0; j < GrdRDocument.Rows.Count; j++)

您可以遍历GrdRDocument中的每个Row，而不管行数或页面大小。这是错误的；您必须在页面填满后停止。顺便说一句，我希望GrdRDocument是不可变数据的本地副本，并且您不会将UI控件传递给打印线程。

s++;
if(s == 10)
{    
    //ev.HasMorePages = true;  //this line doesn't work
    s = 0;

您的注释行将工作得很好。问题是你设置了ev.HasMorePages = true然后忽略了它；你设置了s = 0并继续迭代；下一次迭代s!=10，所以你：

    ev.HasMorePages = false;

请阅读PrintDocument文档；其中有一个打印多页的示例。您应该创建一个类来存储所有非托管资源和页状态。将其设为IDisposable，这样它们就会被处理掉。仅迭代要在每页上打印的行或任何内容。类似于：

class PrintStuff : IDisposable
{
    readonly IEnumerable<Whatever> data;
    readonly PrintDocument pd;
    Font font;
    private int currentIndex;

    public PrintStuff(IEnumerable<Whatever> data)
    {
        this.data = data;

        pd = new PrintDocument();
        pd.BeginPrint += OnBeginPrint;
        pd.PrintPage += OnPrintPage;
        pd.EndPrint += OnEndPrint;
    }

    public void Print()
    {
        pd.Print();
    }

    public void Dispose()
    {
        pd.Dispose();
    }

    private void OnBeginPrint(object sender, PrintEventArgs args)
    {
        font = new Font(FontFamily.GenericSansSerif, 12F);
        currentIndex = 0;
    }

    private void OnEndPrint(object sender, PrintEventArgs args)
    {
        font.Dispose();
    }

    private void OnPrintPage(object sender, PrintPageEventArgs args)
    {
        var x = Convert.ToSingle(args.MarginBounds.Left);
        var y = Convert.ToSingle(args.MarginBounds.Top);
        var lineHeight = font.GetHeight(args.Graphics);
        while ((currentIndex < data.Count())
               && (y <= args.MarginBounds.Bottom))
        {
            args.Graphics.DrawWhatever(data.ElementAt(currentIndex), font, Brushes.Black, x, y);
            y += lineHeight;
            currentIndex++;
        }

        args.HasMorePages = currentIndex < data.Count();
    }
}