这是一个非常奇怪的情况，首先是代码......

编码

 private List<DispatchInvoiceCTNDataModel> WorksheetToDataTableForInvoiceCTN(ExcelWorksheet excelWorksheet, int month, int year)
        {
            int totalRows = excelWorksheet.Dimension.End.Row;
            int totalCols = excelWorksheet.Dimension.End.Column;
            DataTable dt = new DataTable(excelWorksheet.Name);
            // for (int i = 1; i <= totalRows; i++)
            Parallel.For(1, totalRows + 1, (i) =>
            {
                DataRow dr = null;
                if (i > 1)
                {
                    dr = dt.Rows.Add();
                }
                for (int j = 1; j <= totalCols; j++)
                {
                    if (i == 1)
                    {
                        var colName = excelWorksheet.Cells[i, j].Value.ToString().Replace(" ", String.Empty);
                        lock (lockObject)
                        {
                            if (!dt.Columns.Contains(colName))
                                dt.Columns.Add(colName);
                        }
                    }
                    else
                    {
                        dr[j - 1] = excelWorksheet.Cells[i, j].Value != null ? excelWorksheet.Cells[i, j].Value.ToString() : null;
                    }
                }
            });
            var excelDataModel = dt.ToList<DispatchInvoiceCTNDataModel>();
            // now we have mapped everything expect for the IDs
            excelDataModel = MapInvoiceCTNIDs(excelDataModel, month, year, excelWorksheet);
            return excelDataModel;
        }

  dr[j - 1] = excelWorksheet.Cells[i, j].Value != null ? excelWorksheet.Cells[i, j].Value.ToString() : null;

using (var xlPackage = new ExcelPackage(viewModel.postedFile.InputStream))
            {
                ExcelWorksheets worksheets = xlPackage.Workbook.Worksheets;

                // other stuff 
                var entities = this.WorksheetToDataTableForInvoiceCTN(worksheets[1], viewModel.Month, viewModel.Year);
                // other stuff 
            }

  dr = dt.Rows.Add();

  lock(lockObject) {
      dr = dt.Rows.Add();
  }

System.ArgumentOutOfRangeException was unhandled by user code
  HResult=-2146233086
  Message=Index was out of range. Must be non-negative and less than the size of the collection.
Parameter name: index
  Source=mscorlib
  ParamName=index
  StackTrace:
       at System.ThrowHelper.ThrowArgumentOutOfRangeException()
       at System.Collections.Generic.List`1.get_Item(Int32 index)
       at System.Data.RecordManager.NewRecordBase()
       at System.Data.DataTable.NewRecordFromArray(Object[] value)
       at System.Data.DataRowCollection.Add(Object[] values)
       at AdminEntity.BAL.Service.ExcelImportServices.<>c__DisplayClass2e.<WorksheetToDataTableForInvoiceCTN>b__2d(Int32 i) in C:\Projects\Manager\Admin\AdminEntity\AdminEntity.BAL\Service\ExcelImportServices.cs:line 578
       at System.Threading.Tasks.Parallel.<>c__DisplayClassf`1.<ForWorker>b__c()
  InnerException: 

最佳答案

好的。因此，您现有的代码存在一些问题，其中大部分已被其他人触及:

private void ReadIntoTable(ExcelWorksheet sheet)
{
    DataTable dt = new DataTable(sheet.Name);
    int height = sheet.Dimension.Rows;
    int width = sheet.Dimension.Columns;

    for (int j = 1; j <= width; j++)
    {
        string colText = (sheet.Cells[1, j].Value ?? "").ToString();
        dt.Columns.Add(colText);
    }
    for (int i = 2; i <= height; i++)
    {
        dt.Rows.Add();
    }

    Parallel.For(1, height, (i) =>
    {
        var row = dt.Rows[i - 1];
        for (int j = 0; j < width; j++)
        {
            string str = (sheet.Cells[i + 1, j + 1].Value ?? "").ToString();
            row[j] = str;
        }
    });

    // convert to your special Excel data model
    // ...
}

Thread Safety

This type is safe for multithreaded read operations. You must synchronize any write operations.

private static object s_lockObject = "";

private void ReadIntoTable(ExcelWorksheet sheet)
{
    // ...
    lock (s_lockObject)
    {
        row[j] = str;
    }
    // ...
}

string[,] rows = new string[height, width];
Parallel.For(1, height, (i) =>
{
    for (int j = 0; j < width; j++)
    {
        rows[i - 1, j] = (sheet.Cells[i + 1, j + 1].Value ?? "").ToString();
    }
});

关于c# - 使用 ParallelFor 循环时索引超出范围异常，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/29541767/