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C# - Convert all charts in excel spreadsheet to images

I need to be able to convert all charts in an excel spreadsheet to images programmatically (via c#),
I've tried Aspose.cells and it works perfectly, but i need a free alternative.
EPplus and other non-commercial libraries i know do not have the ability to do this,
and i'm in an web environment so I cannot use Office Interop.
My question is: is there any way I can programmatically read an .xlsx file and swap every chart it contains for an image of said chart, without depending on a paid library ?

Try Spire.Xls
var wb = new Spire.Xls.Workbook();
var sheet=wb.Worksheets[0];
//Replace charts with png
var charts = summarySheet.Charts.Select(x => (Chart)x).ToArray();
if (charts.Any())
{
var imgs = wb.SaveChartAsImage(summarySheet); //same indexes as chart obj arr
for (int i = 0; i <= charts.Length - 1; i++)
{
var chart = charts[i];
var chartImg = imgs[i];
summarySheet.Pictures.Add(chart.TopRow, chart.LeftColumn, chartImg, 100, 100, ImageFormatType.Png);
}
}

Have you tried ClosedXML.Excel in nuget?
XLSX support
using (var workbook = new XLWorkbook())
{
var worksheet = workbook.Worksheets.Add("Sample Sheet");
worksheet.Cell("A1").Value = "Hello World!";
worksheet.Cell("A2").FormulaA1 = "=MID(A1, 7, 5)";
workbook.SaveAs("HelloWorld.xlsx");
}
source https://github.com/ClosedXML/ClosedXML

File wont open after saving

I have some code that is suppose to enter some values into several excel workbooks. Right now the program doesn't even put any values into the workbooks and only saves them. Even like this i get this error when opening the files: Excel cannot open the file **.xlsm because the file format or file extension is not valid. Verify that the file has been corrupted and that the file extension matches the format of the file.
I have writen many programs that work with excel files and never had this problem. In the code you can see that i basically just go through a for loop and save the file.
try
{
fileInfo = new FileInfo(Path.GetDirectoryName(Application.StartupPath) + '\\' + partners[partner].partnerName + #"\PDP_ExSumm_" + partners[partner].partnerName + ".xlsm");
using (ExcelPackage excelPackage = new ExcelPackage(fileInfo))
{
ExcelWorksheet worksheet = excelPackage.Workbook.Worksheets[1];
for (int cell = 0; cell < ExSummCells.Count; cell++)
{
if (ExSummCells[cell] != "")
{
// worksheet.Cells[ExSummCells[cell]].Value = partners[partner].exSummData[partner];
}
excelPackage.Save();
}
}

Replacing Invalid XML characters from an excel file and writing it back to disk causes file is corrupted error on opening in MS Excel

A little background on problem:
We have an ASP.NET MVC5 Application where we use FlexMonster to show the data in grid. The data source is a stored procedure that brings all the data into the UI grid, and once user clicks on export button, it exports the report to Excel. However, in some cases export to excel is failing.
Some of the data has some invalid characters, and it is not possible/feasible to fix the source as suggested here
My approach so far:
EPPlus library fails on initializing the workbook as the input excel file contains some invalid XML characters. I could find that the file is dumped with some invalid character in it. I looked into the possible approaches .
Firstly, I identified the problematic character in the excel file. I first tried to replace the invalid character with blank space manually using Notepad++ and the EPPlus could successfully read the file.
Now using the approaches given in other SO thread here and here, I replaced all possible occurrences of invalid chars. I am using at the moment
XmlConvert.IsXmlChar
method to find out the problematic XML character and replacing with blank space.
I created a sample program where I am trying to work on the problematic excel sheet.
//in main method
String readFile = File.ReadAllText(filePath);
string content = RemoveInvalidXmlChars(readFile);
File.WriteAllText(filePath, content);
//removal of invalid characters
static string RemoveInvalidXmlChars(string inputText)
{
StringBuilder withoutInvalidXmlCharsBuilder = new StringBuilder();
int firstOccurenceOfRealData = inputText.IndexOf("<t>");
int lastOccurenceOfRealData = inputText.LastIndexOf("</t>");
if (firstOccurenceOfRealData < 0 ||
lastOccurenceOfRealData < 0 ||
firstOccurenceOfRealData > lastOccurenceOfRealData)
return inputText;
withoutInvalidXmlCharsBuilder.Append(inputText.Substring(0, firstOccurenceOfRealData));
int remaining = lastOccurenceOfRealData - firstOccurenceOfRealData;
string textToCheckFor = inputText.Substring(firstOccurenceOfRealData, remaining);
foreach (char c in textToCheckFor)
{
withoutInvalidXmlCharsBuilder.Append((XmlConvert.IsXmlChar(c)) ? c : ' ');
}
withoutInvalidXmlCharsBuilder.Append(inputText.Substring(lastOccurenceOfRealData));
return withoutInvalidXmlCharsBuilder.ToString();
}
If I replaces the problematic character manually using notepad++, then the file opens fine in MSExcel. The above mentioned code successfully replaces the same invalid character and writes the content back to the file. However, when I try to open the excel file using MS Excel, it throws an error saying that file may have been corrupted and no content is displayed (snapshots below). Moreover, Following code
var excelPackage = new ExcelPackage(new FileInfo(filePath));
on the file that I updated via Notepad++, throws following exception
"CRC error: the file being extracted appears to be corrupted. Expected 0x7478AABE, Actual 0xE9191E00"}
My Questions:
Is my approach to modify content this way correct?
If yes, How can I write updated string to an Excel file?
If my approach is wrong then, How can I proceed to get rid of invalid XML chars?
Errors shown on opening file (without invalid XML char):
First Pop up
When I click on yes
Thanks in advance !

It does sounds like a binary (presumable XLSX) file based on your last comment. To confirm, open the file created by the FlexMonster with 7zip. If it opens properly and you see a bunch of XML files in folders, its a XLSX.
In that case, a search/replace on a binary file sounds like a very bad idea. It might work on the XML parts but might also replace legit chars in other parts. I think the better approach would be to do as #PanagiotisKanavos suggests and use ZipArchive. But you have to do rebuild it in the right order otherwise Excel complains. Similar to how it was done here https://stackoverflow.com/a/33312038/1324284, you could do something like this:
public static void ReplaceXmlString(this ZipArchive xlsxZip, FileInfo outFile, string oldString, string newstring)
{
using (var outStream = outFile.Open(FileMode.Create, FileAccess.ReadWrite))
using (var copiedzip = new ZipArchive(outStream, ZipArchiveMode.Update))
{
//Go though each file in the zip one by one and copy over to the new file - entries need to be in order
foreach (var entry in xlsxZip.Entries)
{
var newentry = copiedzip.CreateEntry(entry.FullName);
var newstream = newentry.Open();
var orgstream = entry.Open();
//Copy non-xml files over
if (!entry.Name.EndsWith(".xml"))
{
orgstream.CopyTo(newstream);
}
else
{
//Load the xml document to manipulate
var xdoc = new XmlDocument();
xdoc.Load(orgstream);
var xml = xdoc.OuterXml.Replace(oldString, newstring);
xdoc = new XmlDocument();
xdoc.LoadXml(xml);
xdoc.Save(newstream);
}
orgstream.Close();
newstream.Flush();
newstream.Close();
}
}
}
When it is used like this:
[TestMethod]
public void ReplaceXmlTest()
{
var datatable = new DataTable("tblData");
datatable.Columns.AddRange(new[]
{
new DataColumn("Col1", typeof (int)),
new DataColumn("Col2", typeof (int)),
new DataColumn("Col3", typeof (string))
});
for (var i = 0; i < 10; i++)
{
var row = datatable.NewRow();
row[0] = i;
row[1] = i * 10;
row[2] = i % 2 == 0 ? "ABCD" : "AXCD";
datatable.Rows.Add(row);
}
using (var pck = new ExcelPackage())
{
var workbook = pck.Workbook;
var worksheet = workbook.Worksheets.Add("source");
worksheet.Cells.LoadFromDataTable(datatable, true);
worksheet.Tables.Add(worksheet.Cells["A1:C11"], "Table1");
//Now similulate the copy/open of the excel file into a zip archive
using (var orginalzip = new ZipArchive(new MemoryStream(pck.GetAsByteArray()), ZipArchiveMode.Read))
{
var fi = new FileInfo(#"c:\temp\ReplaceXmlTest.xlsx");
if (fi.Exists)
fi.Delete();
orginalzip.ReplaceXmlString(fi, "AXCD", "REPLACED!!");
}
}
}
Gives this:
Just keep in mind that this is completely brute force. Anything you can do to make the file filter smarter rather then simply doing ALL xml files would be a very good thing. Maybe limit it to the SharedString.xml file if that is where the problem lies or in the xml files in the worksheet folders. Hard to say without knowing more about the data.

Unable to delete a worksheet using EPPlus

I am using this code:
ExcelPackage pck = new ExcelPackage(newFile);
var wk = pck.Workbook.Worksheets.SingleOrDefault(x => x.Name == "Content");
pck.Workbook.Worksheets.Delete(wk);
But in delete it gives me "IndexOutOfRangeException", but I am trying to delete from object, I have tried to delete by index "1", I just have two worksheets, and the same exception. The file and worksheet is not null, but when I execute delete in anyway I receive the "IndexOutOfRangeException".
What's happening?
Note: I have created this worksheet from ExcelPackage too and now i want delete it.

Looks like you ran into some temporary bug/issue, that was already fixed. As of EpPlus 4.0.1.1, the following code works just fine:
var workbookFileInfo = new FileInfo(#"Workbook.xlsx");
using (var excelPackage = new ExcelPackage(workbookFileInfo))
{
excelPackage.Workbook.Worksheets.Add("Worksheet1");
excelPackage.Workbook.Worksheets.Add("Worksheet2");
excelPackage.Save();
}
using (var excelPackage = new ExcelPackage(workbookFileInfo))
{
var worksheet = excelPackage.Workbook.Worksheets.SingleOrDefault(x => x.Name == "Worksheet1");
excelPackage.Workbook.Worksheets.Delete(worksheet);
excelPackage.Save();
}
Try to update to the latest available stable version of EpPlus and if will not help you, please post additional details applicable for the latest version.

Updating existing excel file while it is open

I read a lot about how to communicate from C# to Excel and saw some good references.
The thing is I'm looking for an easy way to update existing excel file while it is still open, using
the most advanced way (linq for example) and not OLEDB.
This should be few lines of code describing how can I read current cell, update his value and take into consideration the file might not be exist, but if it does exist and open, it will just update the file without giving the notification the file is already exist. If the file doesn't exist it will create a new one.
SO:
1. connect to an excel file, check if it exist, if not create one
2. read from cell
3. update cell
4. do this while the excel sheet can be still open wild.
I already visited the following places:
http://social.msdn.microsoft.com/Forums/vstudio/en-US/ef11a193-54f3-407b-9374-9f5770fd9fd7/writing-to-excel-using-c
Updating an excel document programmatically
Update specific cell of excel file using oledb
I used the following code:
if (File.Exists(#"C:\\temp\\test.xls"))
{
Microsoft.Office.Interop.Excel.Application excelApp = new Microsoft.Office.Interop.Excel.Application();
Microsoft.Office.Interop.Excel.Workbooks workBooks = excelApp.Workbooks;
Microsoft.Office.Interop.Excel.Workbook workBook = workBooks.Open(#"C:\\temp\\test.xls");
Microsoft.Office.Interop.Excel.Worksheet workSheet = workBook.Worksheets.get_Item(1);
int nColumns = workSheet.UsedRange.Columns.Count;
int nRows = workSheet.UsedRange.Rows.Count;
for (int i = 2; i < nRows; i++)
{
workSheet.Columns["1","A"] = "test";
}
workBook.Save();
workBook.Close();
}

So I use VSTO Contrib to help out with COM Interop and memory management and that's why you see .WithComCleanup().
To open up a spreadsheet:
try
{
using (var xlApp = new Microsoft.Office.Interop.Excel.Application().WithComCleanup())
using (var wrkbooks = xlApp.Resource.Workbooks.WithComCleanup())
using (var wrkbook = wrkbooks.Resource.Open(filePath, false, true).WithComCleanup())
{
If the excel file is already open, then to get around the Read-Only follow this tip:
wrkbooks.Resource.Open(filePath, false, FALSE).WithComCleanup())
Here's how I iterate though the sheets (note that some Excel sheets are ChartSheets):
foreach (object possibleSheet in xlApp.Resource.Sheets)
{
Microsoft.Office.Interop.Excel.Worksheet aSheet = possibleSheet as Microsoft.Office.Interop.Excel.Worksheet;
if (aSheet == null)
continue;
Here is a quick way to get a reference to the sheet you're interested in:
activeSheet = wrkbook.Resource.Sheets[sheetToImport];
You read and write to cells just as you've identified:
for (int i = 2; i < nRows; i++)
{
activeSheet.Columns["1","A"] = "test";
}
Here is how I close Excel:
MathematicaAPI.XlHelper.CloseExcel((Worksheet)activeSheet, (Workbook)wrkbook.Resource , (Workbooks)wrkbooks.Resource);
public static void CloseExcel(Worksheet activeSheet, Workbook wrkbook, Workbooks wrkbooks)
{
//http://support.microsoft.com/kb/317109 -> excel just wont close for some reason
if (activeSheet != null)
{
Marshal.FinalReleaseComObject(activeSheet);
activeSheet = null;
}
if (wrkbook != null)
{
wrkbook.Saved = true;
wrkbook.Close(Microsoft.Office.Interop.Excel.XlSaveAction.xlDoNotSaveChanges);
}
if (wrkbooks != null)
{
wrkbooks.Close();
}
GC.Collect();
GC.WaitForPendingFinalizers();
GC.Collect();
GC.WaitForPendingFinalizers();
}
Sometimes Excel just wont close and you have to kill it (after trying to close it properly of course) - I dont recommend this, but if you cant track down the un-disposed memory and all else fails then...
if (xlApp != null)
{
ExcelDataSourceHelper.GetWindowThreadProcessId(new IntPtr(xlApp.Resource.Hwnd), ref excelProcessId);
}
if (excelProcessId > 0)
{
XlHelper.KillProcess(excelProcessId);
}
public static void KillProcess(int excelProcessId)
{
if (excelProcessId > 0)
{
System.Diagnostics.Process ExcelProc = null;
try
{
ExcelProc = System.Diagnostics.Process.GetProcessById(excelProcessId);
if (ExcelProc != null)
{
ExcelProc.Kill();
}
}
catch
{ }
}
}
Note: I reduce the chances of needing to kill Excel by using VSTO Contrib with Using's.

OK thank you all for trying to solve the issue
The solution was using Excel 2011/2013 Add-In which can communicate excel as a plugin
create an application-level add-in for Microsoft Office Excel. The features that you create in this kind of solution are available to the application itself, regardless of which workbooks are open.
You can visit MSDN