如何加快将DataTable转储到Excel工作表？

Question

我有以下例程将DataTable转储到Excel工作表中.

    private void RenderDataTableOnXlSheet(DataTable dt, Excel.Worksheet xlWk, 
                                    string [] columnNames, string [] fieldNames)
    {
        // render the column names (e.g. headers)
        for (int i = 0; i < columnNames.Length; i++)
            xlWk.Cells[1, i + 1] = columnNames[i];

        // render the data 
        for (int i = 0; i < fieldNames.Length; i++)
        {
            for (int j = 0; j < dt.Rows.Count; j++)
            {
                xlWk.Cells[j + 2, i + 1] = dt.Rows[j][fieldNames[i]].ToString();
            }
        }
    }

无论出于何种原因,在我相对现代的PC上倾销25列和400行的DataTable大约需要10-15秒.占用更长的测试人员的机器.

我有什么办法可以加快这段代码的速度吗？或者互操作本身就很慢？

解决方案:根据Helen Toomik的建议,我修改了方法,它现在应该适用于几种常见的数据类型(int32,double,datetime,string).随意扩展它.处理我的数据集的速度从15秒变为1秒.

    private void RenderDataTableOnXlSheet(DataTable dt, Excel.Worksheet xlWk, string [] columnNames, string [] fieldNames)
    {
        Excel.Range rngExcel = null;
        Excel.Range headerRange = null;

        try
        {
            // render the column names (e.g. headers)
            for (int i = 0; i < columnNames.Length; i++)
                xlWk.Cells[1, i + 1] = columnNames[i];

            // for each column, create an array and set the array 
            // to the excel range for that column.
            for (int i = 0; i < fieldNames.Length; i++)
            {
                string[,] clnDataString = new string[dt.Rows.Count, 1];
                int[,] clnDataInt = new int[dt.Rows.Count, 1];
                double[,] clnDataDouble = new double[dt.Rows.Count, 1];

                string columnLetter = char.ConvertFromUtf32("A".ToCharArray()[0] + i);
                rngExcel = xlWk.get_Range(columnLetter + "2", Missing.Value);
                rngExcel = rngExcel.get_Resize(dt.Rows.Count, 1);

                string dataTypeName = dt.Columns[fieldNames[i]].DataType.Name;

                for (int j = 0; j < dt.Rows.Count; j++)
                {
                    if (fieldNames[i].Length > 0)
                    {
                        switch (dataTypeName)
                        {
                            case "Int32":
                                clnDataInt[j, 0] = Convert.ToInt32(dt.Rows[j][fieldNames[i]]);
                                break;
                            case "Double":
                                clnDataDouble[j, 0] = Convert.ToDouble(dt.Rows[j][fieldNames[i]]);
                                break;
                            case "DateTime":
                                if (fieldNames[i].ToLower().Contains("time"))
                                    clnDataString[j, 0] = Convert.ToDateTime(dt.Rows[j][fieldNames[i]]).ToShortTimeString();
                                else if (fieldNames[i].ToLower().Contains("date"))
                                    clnDataString[j, 0] = Convert.ToDateTime(dt.Rows[j][fieldNames[i]]).ToShortDateString();
                                else 
                                    clnDataString[j, 0] = Convert.ToDateTime(dt.Rows[j][fieldNames[i]]).ToString();

                                break;
                            default:
                                clnDataString[j, 0] = dt.Rows[j][fieldNames[i]].ToString();
                                break;
                        }
                    }
                    else
                        clnDataString[j, 0] = string.Empty;
                }

                // set values in the sheet wholesale.
                if (dataTypeName == "Int32") 
                    rngExcel.set_Value(Missing.Value, clnDataInt);
                else if (dataTypeName == "Double")
                    rngExcel.set_Value(Missing.Value, clnDataDouble);                             
                else
                    rngExcel.set_Value(Missing.Value, clnDataString);
            }


            // figure out the letter of the last column (supports 1 letter column names)
            string lastColumn = char.ConvertFromUtf32("A".ToCharArray()[0] + columnNames.Length - 1);

            // make the header range bold
            headerRange = xlWk.get_Range("A1", lastColumn + "1");
            headerRange.Font.Bold = true;

            // autofit for better view
            xlWk.Columns.AutoFit();

        }
        finally
        {
            ReleaseObject(headerRange);
            ReleaseObject(rngExcel);
        }
    }

    private void ReleaseObject(object obj)
    {
        try
        {
            System.Runtime.InteropServices.Marshal.ReleaseComObject(obj);
            obj = null;
        }
        catch
        {
            obj = null;
        }
        finally
        {
            GC.Collect();
        }
    }

Answer 1

而不是逐个设置单元格值,而是批量执行.

步骤1.将数据从DataTable传输到具有相同尺寸的阵列.

步骤2.定义跨越适当范围的Excel范围对象.

步骤3.将Range.Value设置为数组.

这将快得多,因为你将在Interop边界上有两个调用(一个用于获取Range对象,一个用于设置其值),而不是每个单元格两个(获取单元格,设置值).

MSDN知识库文章302096中有一些示例代码.