[英]How can a base class with abstract methods be used to handle delegate calls?
這是基類:
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));
}
}
這是具體的實現:
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));
}
}
有兩個問題:
DataResult
由Visual Studio 2008中無法識別,即使是在ReportWinForm基類。 Form
后代,也不能編輯從ReportWinForm派生的類。 有關更多上下文,請參見委托如何使用通用且可擴展的類響應多個事件?
即使在ReportWinForm基類中,Visual Studio 2008也無法識別DataResult。
如果確實在類中,則應在類外部指定ReportWinForm.DataResult
。
VS 2008中的設計器聲稱,即使基類是Form的后代,也不能編輯從ReportWinForm派生的類。
您確定所有DLL依賴項都正確嗎? 您需要在其中定義了所有基類的所有DLL。
順便說一句,如果可以並且想要升級,則可以免費下載Visual Studio 2012 Express版 。
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