使用 EPPlus 复制/克隆 Excel 图表

Question

I'm using EPPlus in my project and I know you can copy an existing Shape however there is no method for copying an existing Chart.

I have setup a workbook with template charts that I need to duplicate and update the series to point to different datatable/sets.

I can populate the data no worries and can create new charts, but then need to size and position and style. It would be a lot easier to just clone the chart template and modify series and position to simplify the code.

Currently I use this approach:

// wb is an ExcelWorkbook
ExcelWorksheet ws = wb.Worksheets[sheetIdx];
ExcelChart chart = (ExcelChart)ws.Drawings[0];
ExcelChart cc = ws.Drawings.AddChart("Chart " + (i + 2), eChartType.ColumnClustered);

// invoke methods that will position and size new chart

// copy starting chart xml so will have identical styling, series, legend etc
var xml = XDocument.Parse(chart.ChartXml.InnerXml);
XNamespace nsC = "http://schemas.openxmlformats.org/drawingml/2006/chart";
XNamespace nsA = "http://schemas.openxmlformats.org/drawingml/2006/main";

// modify xml to update Category, Title and Values formulas
var fs = xml.Descendants(nsC + "f");
foreach (var f in fs)
{
    f.Value = ws.Cells[f.Value].Offset(chartNumRows + 1, 0).FullAddressAbsolute;
}

// set new chart xml to modified xml.
cc.ChartXml.InnerXml = xml.ToString();

Which works, but there are several drawbacks.

1) The chart.series of the clone (cc in my example) has not been set, peeking at the code this is because it is only done during the object construction. If I could get this property to update then I would be able to easily resolve the second issue

2) I need to remove all series and add new ones and because the series property isn't initialised properly this is harder than it should be.

Any help getting properties to initialise in the chart or a better method of cloning the original would be greatly appreciated!

Answer 1

It seems like there is no built-in functionality for this and an other reload methods I could come up with required too many changes to the EPPlus source, so until I find a better solution I have added the following method to EPPlus\\Drawings\\ExcelDrawings.cs

public ExcelChart CloneChart(ExcelChart SourceChart, String NewName)
{
    // Create clone
    var tempClone = this.AddChart(NewName, SourceChart.ChartType, null);
    tempClone.ChartXml.InnerXml = SourceChart.ChartXml.InnerXml;

    // Reload clone
    using (tempClone.Part.Stream = new MemoryStream())
    {
        // Create chart object using temps package and xml
        var chartXmlBytes = Encoding.ASCII.GetBytes(tempClone.ChartXml.OuterXml);
        tempClone.Part.Stream.Write(chartXmlBytes, 0, chartXmlBytes.Length);
        var finalClone = ExcelChart.GetChart(this, tempClone.TopNode);

        // Remove old from collection
        var index = _drawingNames[tempClone.Name];
        var draw = _drawings[index];
        for (int i = index + 1; i < _drawings.Count; i++)
            _drawingNames[_drawings[i].Name]--;
        _drawingNames.Remove(draw.Name);
        _drawings.Remove(draw);

        // Add new to collection
        finalClone.Name = tempClone.Name;
        _drawings.Add(finalClone);
        _drawingNames.Add(finalClone.Name, _drawings.Count - 1);

        // Done
        return finalClone;
    }
}