具有抽象方法的基类如何用于处理委托调用？

Question

这是基类：

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using Microsoft.Reporting.WinForms;

abstract class ReportWinForm : System.Windows.Forms.Form
{
    // This will be the one line of code needed in each WinForm--providing the base class a reference
    //  to the report, so it has access to the SubreportProcessing event
    protected ReportViewer WinFormReportViewer { get; set; }

    // Making this abstract requires each derived WinForm to implement GetReportData--foolproof!

    protected abstract DataResult GetReportData(SubreportProcessingEventArgs e);

    // Wire up the subreport_processing handler when any WinForm loads
    // You could override this in derived WinForms classes if you need different behavior for some WinForms,
    //  but I would bet this default behavior will serve well in most or all cases
    protected virtual void Form1_Load(object sender, EventArgs e)
    {
        WinFormReportViewer.LocalReport.SubreportProcessing += new SubreportProcessingEventHandler(LocalReport_SubreportProcessing);

    }

    // When the Subreport processing event fires, handle it here
    // You could also override this method in a derived class if need be
    protected virtual void LocalReport_SubreportProcessing(object sender, SubreportProcessingEventArgs e)
    {
        // Get the data needed for the subreport
        DataResult dataResult = this.GetReportData(e);

        e.DataSources.Clear();
        e.DataSources.Add(new ReportDataSource(dataResult.Label, dataResult.Table));
    }
}

这是具体的实现：

public frmTestAllView()
{
    //base.WinFormReportViewer = reportViewer1; //Hook-up callbacks to the base class      ReportWinForm
    InitializeComponent();
}

private void frmTestAllView_Load(object sender, EventArgs e)
{
    // TODO: This line of code loads data into the 'AFC_ObsolescenceDataSet.up_Fill_frmInternalCaseStatus_All' table. You can move, or remove it, as needed.
    this.up_Fill_frmInternalCaseStatus_AllTableAdapter.Fill(this.AFC_ObsolescenceDataSet.up_Fill_frmInternalCaseStatus_All);

    this.reportViewer1.RefreshReport();
}

// The search parameters will be different for every winform, and will presumably
//  come from some winform UI elements on that form, e.g., parentPartTextBox.Text
protected override DataResult GetReportData(SubreportProcessingEventArgs e)
{
    // Return the data result, which contains a data table and a label which will be
    //  passed to the report data source
    // You could use DataSet in DataResult instead of DataTable if needed
    switch (e.ReportPath)
    {
        case "rptSubAlternateParts":
            return new DataResult(
                new BLL.AlternatePartBLL().GetAlternativePart(parentPartTextBox.Text)
                , "BLL_AlternatePartBLL"
            );

        case "rptSubGetAssemblies":
            return new DataResult(
                new BLL.SubAssemblyBLL().GetSubAssemblies(someOtherTextBox.Text)
                , "BLL_SubAssemblyBLL"
            );

        default:
            throw new NotImplementedException(string.Format("Subreport {0} is not implemented", e.ReportPath));

    }
}

有两个问题：

1. DataResult由Visual Studio 2008中无法识别，即使是在ReportWinForm基类。
2. VS 2008中的设计器声称，即使基类是Form后代，也不能编辑从ReportWinForm派生的类。

有关更多上下文，请参见委托如何使用通用且可扩展的类响应多个事件？

Answer 1

即使在ReportWinForm基类中，Visual Studio 2008也无法识别DataResult。

如果确实在类中，则应在类外部指定ReportWinForm.DataResult 。

VS 2008中的设计器声称，即使基类是Form的后代，也不能编辑从ReportWinForm派生的类。

您确定所有DLL依赖项都正确吗？ 您需要在其中定义了所有基类的所有DLL。

_{顺便说一句，如果可以并且想要升级，则可以免费下载Visual Studio 2012 Express版 。}