为什么 EPPlus 在访问工作簿时抛出空引用异常
Why is EPPlus Throwing Null Reference Exception on Accessing Workbook
我正在使用 C# .NET Core 2.2 进行编码。我试图在我的代码中用 EPPlusCore 替换 Excel Interop,以提高可靠性和可移植性。我有一系列使用 EPPlus 打开的发票,但其中一些在访问 Excel 包的工作簿 属性 时抛出 "Null Reference" 异常。
这只发生在 运行未调试代码的情况下。调试时,如果我将鼠标悬停在 ExcelPackage 项目上,它会刷新对工作簿的引用,并且我能够 运行 其余代码。
public object[,] GetExcelDataEpplus(string filePath, int index,
bool sheetByName = false, string name = null, string password = null)
{
var remoteFileInfo = new FileInfo(filePath);
if (!remoteFileInfo.Exists)
{
throw new Exception("File does not exist: " + filePath);
}
var currentPath = Path.Combine(AppDomain.CurrentDomain.BaseDirectory, "temp-excel");
if (!Directory.Exists(currentPath))
{
Directory.CreateDirectory(currentPath);
}
var localFileInfo = new FileInfo(Path.Combine(currentPath, remoteFileInfo.Name));
if (!localFileInfo.Exists)
{
File.Copy(filePath, localFileInfo.FullName);
}
object[,] values = null;
try
{
if (!File.Exists(localFileInfo.FullName))
{
_logger.LogInformation(DbLog, "Cannot find file : " + localFileInfo.FullName);
return null;
}
else
{
_logger.LogInformation(DbLog, "Found file : " + localFileInfo.FullName);
}
_logger.LogInformation(DbLog, "Initializing EPPlus...");
using (var package = string.IsNullOrEmpty(password)
? new ExcelPackage(localFileInfo)
: new ExcelPackage(localFileInfo, password))
{
_logger.LogInformation(DbLog, "Opening Workbook...");
//todo Error Thrown Here
try
{
package.Workbook.FormulaParserManager.LoadFunctionModule(new ImporterFunctionModule());
}
catch (Exception e)
{
_logger.LogWarning(DbLog, e, $"Could not load workbook : Loading file again...");
try
{
System.Threading.Thread.Sleep(1000);
package.Workbook.FormulaParserManager.LoadFunctionModule(new ImporterFunctionModule());
}
catch (Exception ex)
{
_logger.LogError(DbLog, ex, "Could not load workbook");
throw;
}
}
var workbook = package.Workbook;
_logger.LogInformation(DbLog, $"Calculating formulas...");
workbook.Calculate();
_logger.LogInformation(DbLog, "Finding Worksheet...");
var worksheet = sheetByName ? workbook.Worksheets.FirstOrDefault(x => x.Name == name) : workbook.Worksheets[index];
if (worksheet == null)
{
throw new Exception($"Could not find worksheet : {name}");
}
_logger.LogInformation(DbLog, $"Reading from worksheet : {worksheet.Name}...");
var start = worksheet.Dimension.Start;
var end = worksheet.Dimension.End;
values = worksheet.Cells[start.Row, start.Column, end.Row, end.Column].ToMultiDimensionalArray();
}
}
catch (Exception e)
{
_logger.LogError(DbLog, e, $"GetExcelInvoiceDataEpplus from {filePath} ({localFileInfo.FullName})"); //todo propogate error
}
finally
{
File.Delete(localFileInfo.FullName);
}
var rowCount = values?.GetLength(0) ?? 0;
_logger.LogInformation(DbLog, $"EPPLus found {rowCount} rows in the spreadsheet");
return values;
}
在大多数文件上,这都能正常工作,并且我从指定的工作表选项卡中获得了值的多维数组。但是,在某些文件上,它不起作用,我不知道为什么。
我能找到的最接近的类似问题是:https://github.com/JanKallman/EPPlus/issues/416
但如果这是准确的,我怎么知道哪些工作表名称有错误引用而不先访问工作簿?
我找到了解决方案。 excel 个有问题的文件是大于平均水平的文件。
解决办法就是多等他们一段时间。
try
{
package.Workbook.FormulaParserManager.LoadFunctionModule(new ImporterFunctionModule());
}
catch (Exception e)
{
for (var i=1; i < 6; i++)
{
_logger.LogWarning(DbLog, e, $"Could not load workbook : Loading file again (Attempt #{i})...");
try
{
System.Threading.Thread.Sleep(2000);
package.Workbook.FormulaParserManager.LoadFunctionModule(new ImporterFunctionModule());
break;
}
catch (Exception ex)
{
if (i < 5) continue;
_logger.LogError(DbLog, ex, "Could not load workbook after 5 attempts");
throw;
}
}
}
我正在使用 C# .NET Core 2.2 进行编码。我试图在我的代码中用 EPPlusCore 替换 Excel Interop,以提高可靠性和可移植性。我有一系列使用 EPPlus 打开的发票,但其中一些在访问 Excel 包的工作簿 属性 时抛出 "Null Reference" 异常。
这只发生在 运行未调试代码的情况下。调试时,如果我将鼠标悬停在 ExcelPackage 项目上,它会刷新对工作簿的引用,并且我能够 运行 其余代码。
public object[,] GetExcelDataEpplus(string filePath, int index,
bool sheetByName = false, string name = null, string password = null)
{
var remoteFileInfo = new FileInfo(filePath);
if (!remoteFileInfo.Exists)
{
throw new Exception("File does not exist: " + filePath);
}
var currentPath = Path.Combine(AppDomain.CurrentDomain.BaseDirectory, "temp-excel");
if (!Directory.Exists(currentPath))
{
Directory.CreateDirectory(currentPath);
}
var localFileInfo = new FileInfo(Path.Combine(currentPath, remoteFileInfo.Name));
if (!localFileInfo.Exists)
{
File.Copy(filePath, localFileInfo.FullName);
}
object[,] values = null;
try
{
if (!File.Exists(localFileInfo.FullName))
{
_logger.LogInformation(DbLog, "Cannot find file : " + localFileInfo.FullName);
return null;
}
else
{
_logger.LogInformation(DbLog, "Found file : " + localFileInfo.FullName);
}
_logger.LogInformation(DbLog, "Initializing EPPlus...");
using (var package = string.IsNullOrEmpty(password)
? new ExcelPackage(localFileInfo)
: new ExcelPackage(localFileInfo, password))
{
_logger.LogInformation(DbLog, "Opening Workbook...");
//todo Error Thrown Here
try
{
package.Workbook.FormulaParserManager.LoadFunctionModule(new ImporterFunctionModule());
}
catch (Exception e)
{
_logger.LogWarning(DbLog, e, $"Could not load workbook : Loading file again...");
try
{
System.Threading.Thread.Sleep(1000);
package.Workbook.FormulaParserManager.LoadFunctionModule(new ImporterFunctionModule());
}
catch (Exception ex)
{
_logger.LogError(DbLog, ex, "Could not load workbook");
throw;
}
}
var workbook = package.Workbook;
_logger.LogInformation(DbLog, $"Calculating formulas...");
workbook.Calculate();
_logger.LogInformation(DbLog, "Finding Worksheet...");
var worksheet = sheetByName ? workbook.Worksheets.FirstOrDefault(x => x.Name == name) : workbook.Worksheets[index];
if (worksheet == null)
{
throw new Exception($"Could not find worksheet : {name}");
}
_logger.LogInformation(DbLog, $"Reading from worksheet : {worksheet.Name}...");
var start = worksheet.Dimension.Start;
var end = worksheet.Dimension.End;
values = worksheet.Cells[start.Row, start.Column, end.Row, end.Column].ToMultiDimensionalArray();
}
}
catch (Exception e)
{
_logger.LogError(DbLog, e, $"GetExcelInvoiceDataEpplus from {filePath} ({localFileInfo.FullName})"); //todo propogate error
}
finally
{
File.Delete(localFileInfo.FullName);
}
var rowCount = values?.GetLength(0) ?? 0;
_logger.LogInformation(DbLog, $"EPPLus found {rowCount} rows in the spreadsheet");
return values;
}
在大多数文件上,这都能正常工作,并且我从指定的工作表选项卡中获得了值的多维数组。但是,在某些文件上,它不起作用,我不知道为什么。
我能找到的最接近的类似问题是:https://github.com/JanKallman/EPPlus/issues/416
但如果这是准确的,我怎么知道哪些工作表名称有错误引用而不先访问工作簿?
我找到了解决方案。 excel 个有问题的文件是大于平均水平的文件。
解决办法就是多等他们一段时间。
try
{
package.Workbook.FormulaParserManager.LoadFunctionModule(new ImporterFunctionModule());
}
catch (Exception e)
{
for (var i=1; i < 6; i++)
{
_logger.LogWarning(DbLog, e, $"Could not load workbook : Loading file again (Attempt #{i})...");
try
{
System.Threading.Thread.Sleep(2000);
package.Workbook.FormulaParserManager.LoadFunctionModule(new ImporterFunctionModule());
break;
}
catch (Exception ex)
{
if (i < 5) continue;
_logger.LogError(DbLog, ex, "Could not load workbook after 5 attempts");
throw;
}
}
}