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Get current cell value from open Excel sheet using C#

I have an open instance of Excel which is already connected to via a COM process, which I have changed the value of one of the cells. In C# I can't get a connection to the sheet, but in python i can
Working Python code:
import xlwings as xw
wb = xw.Book('c:/users/me/Desktop/mysheet.xlsx')
sheet = wb.sheets['Sheet1']
print(sheet.range('B1').value) # returns the current value
Non-working C# code:
var xlApp = (Application)System.Runtime.InteropServices.Marshal.GetActiveObject("Excel.Application");
Workbook wb = xlApp.ActiveWorkbook; // returns null
Worksheet excelSheet = wb.ActiveSheet;
string test = excelSheet.Cells[1, 2].Value.ToString();
Is there a way to get C# to connect to this sheet, given it is already open via a COM automation from another software product?
Most of the online discussion around GetActiveObject is to talk to a specific instance of Excel if there are multiple instances running, I have the opposite problem, a single instance of Excel and multiple applications trying to connect to it.

Workbook wb = System.Runtime.InteropServices.Marshal.BindToMoniker(#"c:\users\me\Desktop\mysheet.xlsx") as Workbook;
should get the workbook even if it is already opened in Excel or not.
https://blogs.msdn.microsoft.com/eric_carter/2009/03/12/attaching-to-an-already-running-office-application-from-your-application-using-getactiveobject-or-bindtomoniker/

automatically enabling macros in excel c#

I am accessing data from an embedded excel sheet through c#, but in order for the script to read the excel sheet I must manually press "enable macros" every time. How can I write a script such that it automatically enables macros every time? I am opening various excels so cannot change the settings on the excel sheet itself.
I saw something regarding the use of VBA but am unsure what to do? Would using this reference (using VBA = Microsoft.Vbe.Interop) be helpful?
The code below simply opens the excel, but I still have to click enable macros.
using Excel = Microsoft.Office.Interop.Excel;
using Word = Microsoft.Office.Interop.Word;
wordApp = new Word.Application();
xlApp = new Excel.Application();
wordDoc = wordApp.Documents.Open(#"Y:DocumentName");
Word.InlineShapes ils = wordDoc.InlineShapes;
ils[1].OLEFormat.Activate();
xlWorkBook = ils[1].OLEFormat.Object;

Have you tried setting the DisplayAlerts property to false?
xlApp.DisplayAlerts = false;

Using the COM for opening Excel, can't select a particular sheet

I am using the COM to work with Excel 2007. When I use the following code, it opens to the first sheet by default.
Excel = Sys.OleObject("Excel.Application");
Delay (3000); // Wait until Excel starts
Excel.Visible = true;
Excel.Workbooks.Open("G:\\Documentation\\CalCit Excel Files\\2004 Test Data v3 FINAL_new.xlsx");
I need to select different sheets. I tryed using the following code from the DDTdriver code.
Excel = Sys.OleObject("Excel.Application");
Delay (3000); // Wait until Excel starts
Excel.Visible = true;
Excel.Workbooks.Open("G:\\Documentation\\CalCit Excel Files\\2004 Test Data v3 FINAL_new.xlsx", "sheet2", true);
But this does not work. I have tryed many other configs and still get nothing.

For Excel version 2013 or later :
According to learn.microsoft.com
this can be done with Sheets.Select method :
((Excel.Worksheet)this.Application.ActiveWorkbook.Sheets[1]).Select();
which in the code the selected sheet is 1
another method for older versions of Excel :
Excel.Worksheet sheet = (Excel.Worksheet)this.Sheets["Sheet2"];
sheet.Select(Type.Missing);
where Sheet2 is the name of the sheet

C# generating excel file and writing to cells

I am working on a project that runs MySQL queries on DB. I need to feed out the results to a excel sheet that I will be generating on the fly. I had started the code, using msdn tutorials as well as information I found on stackoverflow, however running the application leaves me with
"Object reference not set to an instance of an object."
At this point I just have the basic code started as I wanted to make this work before I started creating the entire spreadsheet in the code.
var excelApp = new Excel.Application();
excelApp.Visible = true;
Excel.Worksheet workSheet = (Excel.Worksheet)excelApp.ActiveSheet;
((Excel.Range)workSheet.Cells[1, 1]).Value = "Print Date:";
If I can provide any more info just ask. I greatly appreciate any information or insight you can provide me with!

I'd say that workSheet is being set to null as excelApp.ActiveSheet doesn't exist yet.
Here's some code that'll create a worksheet object you can use...
var application = new Application();
var workbooks = application.Workbooks;
var workbook = workbooks.Add(XlWBATemplate.xlWBATWorksheet);
var worksheets = (Sheets)workbook.Worksheets;
var worksheet = worksheets[1];
A few things to note when working with Excel:
Release every object with System.Runtime.InteropServices.Marshal.ReleaseComObject(object) when you're finished with it. If you don't, Excel won't exit when you're done.
Don't use double-dot references (i.e., object1.object2.value). If you do you can't release it properly as above.
Indexes always start from 1, not 0 (in my experience anyway).

The reason you get that error is, you have not created any worksheets in the Application.
Try doing this.
Excel.Worksheet newWorksheet;
newWorksheet = (Excel.Worksheet)excelApp.Worksheets.Add();

How to Save/Overwrite existing Excel file with Excel Interop - C#

Is there a way to save changes to an excel spreadsheet through the excel interop (in this case I am adding a worksheet to it) without having it prompt the user if they want to overwrite the existing file with the changes. I do not want the user to even see the spreadsheet open in my application so having a message box popping up asking them if they want to overwrite the file seems very out of place and possibly confusing to the user.
I am using the workbook.SaveAs(fileloaction) method.
Here is where I am initializing the COM reference objects for the excel interop.
private Excel.Application app = null;
private Excel.Workbook workbook = null;
public Excel.Workbook Workbook
{
get { return workbook; }
set { workbook = value; }
}
private Excel.Worksheet worksheet = null;
private Excel.Range workSheet_range = null;
Below is the code I am using to close/save the excel file. The workbook.close() method line is the one that is reportedly throwing the unhandled exception.
workbook.Close(true, startForm.excelFileLocation, Missing.Value);
Marshal.ReleaseComObject(app);
app = null;
System.GC.Collect();

Basically, all you need is ExcelApp.DisplayAlerts = False - Here's how I do it, though:
ExcelApp.DisplayAlerts = False
ExcelWorkbook.Close(SaveChanges:=True, Filename:=CurDir & FileToSave)
Hope this helps

Only this code will Require for stop override alert or Template already in use
ExcelApp.DisplayAlerts = False

I know this is an old post, but I wanted to share a way to make this work without causing possible frustration in the future.
First what I do not like about using: ExcelApp.DisplayAlerts = False
Setting this flag will set this property on the excel file, not just in your program. This means that if a user makes changes to the file and closes it (by clicking the X), they will not be prompted to save the file and will cause frustration later. It will also disable any other prompts excel would typically post.
I like checking if the file exists before saving it:
if (File.Exists(SaveAsName))
{
File.Delete(SaveAsName);
}