C#調(diào)用Delphi編寫的Dll，實現(xiàn)繪圖的功能

以前用Delphi開發(fā)的項目中，會經(jīng)常用到TChart這個畫圖控件，它本身很強大，支持各類圖，如點線圖，柏拉圖，柱狀圖等等，加上可以輸出成BMP，JPEG，JPG，SVG，GIF等各種格式圖片，很好用，當(dāng)時也封裝成比較獨立的DLL文件。這次開發(fā).NET程序正好派上用場，

幾個關(guān)鍵技術(shù)點：
1 C#要以非托管方式調(diào)用DLL
2 C#把整理好的畫圖數(shù)據(jù)生成事先定義好格式的XML文件，傳給DLL
3 DLL解析XML文件，根據(jù)相應(yīng)格式，要求，畫圖
4 DLL輸出GIF文件（經(jīng)過比較GIF圖像失真率小，且文件大小最小）
5 C#裝載GIF文件，傳到前臺展示

關(guān)鍵代碼：
C#

        #region 定義調(diào)用Delphi寫的畫圖DLL
        /// <summary>
        /// 定義調(diào)用Delphi寫的畫圖DLL
        /// </summary>
        private class DrawChartFromDll
        {
            //定義DLL文件名，此文件路徑要加到系統(tǒng)Path中
            private const string _fileDll = @"Chart.dll";
            //調(diào)用非托管Dll，GetChartFromXMLByNet是ChartAccess.dll公開的函數(shù)名稱
            [DllImport(_fileDll, EntryPoint = "GetChartFromXMLByNet", CharSet = CharSet.Ansi, CallingConvention = CallingConvention.StdCall)]
            //C#中的申明
            public static extern int GetChartFromXMLByNet(int piChartType, string psXMLFileName, string psPriChartFileName, string psSecChartFileName, string psPriHotFileName, string psSecHotFileName);
        }
        #endregion            
               
        public ChartResultData GetCharts(ChartData _ChartData, Hashtable _HotPriAdditionSeqNo, Hashtable _HotSecAdditionSeqNo)
        {
            //根據(jù)數(shù)據(jù)生成XML文件
            string _xmlFileName = "";
            ChartResultData _ChartResultData = new ChartResultData();
            try
            {
               _xmlFileName = this.ConvertDataToXml(_ChartData);
            }
            catch (Exception err)
            {
                _ChartResultData.ErrMessage = err.Message;
            }

            ...

            //調(diào)用DELPHI，取得返回參數(shù)
            int _return = -1;
            try
            {                          
                _return = DrawChartFromDll.GetChartFromXMLByNet(m_chartType, _xmlFileName, _priChartFileName, _secChartFileName, _priHotFileName, _secHotFileName);
            }
            catch (Exception err)
            {               
                if (_return > 0)
                {
                    //刪除臨時生成的XML文件
                    this.DeleteTempFile(_xmlFileName);
                    this.DeleteTempFile(_priChartFileName);
                    this.DeleteTempFile(_secChartFileName);
                    this.DeleteTempFile(_priHotFileName);
                    this.DeleteTempFile(_secHotFileName);

                    _ChartResultData.ErrMessage = err.Message;
                    return _ChartResultData;
                }
                else
                {
                    //可能因為安全性問題，在頻繁連續(xù)調(diào)用DLL方法時有可能出現(xiàn)內(nèi)存保護錯誤信息，雖然出錯，但方法已經(jīng)正確調(diào)用并能返回正確的值，此時可以忽略此錯誤
                    _return = 0;
                }
            }

            //刪除臨時生成的XML文件
            this.DeleteTempFile(_xmlFileName);
           
            ...
        }