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c# excel how to Find First Cell in a used range.

I can use XlCellType.xlCellTypeLastCell to find last cell in the used range. How to get first cell in one line ?
Code to get last cell position.
Excel.Range mergeCells = (Excel.Range)mergeSheet.Cells[6,1].EntireRow;
var rowRng = mergeCells.SpecialCells(XlCellType.xlCellTypeLastCell, Type.Missing);
var colPosition = rowRng.Column;
One way is to get mergeCells.value and loop through to increment a counter until I see null/empty value. But I was hoping to get this in one line.
Any ideas ?
Test Cases:
(1)
Expected Result colPosition = 1
(2)
Expected Result colPosition = 5

Here is a solution using the Excel Interop library (as tagged in the question). The below method will return a 1-based column index of the first cell in a given row. It worked for me on your supplied test cases as well as a few of my own. Note that if you wish to simply use the first row in the used range - rather than a supplied row, you can find the first used row number using ActiveSheet.UsedRange.Rows[1].Row.
public static int FindFirstCellInExcelRow(string filePath, int rowNum)
{
Excel.Application xlApp = null;
Excel.Workbook wkBook = null;
Excel.Worksheet wkSheet = null;
Excel.Range range = null;
try
{
xlApp = new Excel.Application();
wkBook = xlApp.Workbooks.Open(filePath);
wkSheet = wkBook.ActiveSheet;
range = wkSheet.Cells[rowNum, 1].EntireRow;
if (range.Cells[1, 1].Value != null)
{
return range.Cells[1, 1].Column;
}
var result = range.Find(What: "*", After: range.Cells[1, 1], LookAt: Excel.XlLookAt.xlPart, LookIn: Excel.XlFindLookIn.xlValues, SearchOrder: Excel.XlSearchOrder.xlByColumns, SearchDirection: Excel.XlSearchDirection.xlNext, MatchByte: false, MatchCase: false);
int colIdx = result?.Column ?? 0; // return 0 if no cell in row contains value
return colIdx;
}
finally
{
wkBook.Close();
Marshal.ReleaseComObject(xlApp);
Marshal.ReleaseComObject(wkBook);
Marshal.ReleaseComObject(wkSheet);
Marshal.ReleaseComObject(range);
xlApp = null;
wkBook = null;
wkSheet = null;
range = null;
}
}

I highly (x10) recommend using ClosedXML over Microsoft's Excel libraries (unless you are using the old xls files). Using ClosedXML you would do the following (this is taken right from their webpage):
Get it right off the NuGet packages. Install-Package ClosedXML -Version 0.93.1
https://github.com/ClosedXML/ClosedXML/wiki/Finding-and-extracting-the-data
var wb = new XLWorkbook(northwinddataXlsx);
var ws = wb.Worksheet("Data");
// Look for the first row used
var firstRowUsed = ws.FirstRowUsed();
// Narrow down the row so that it only includes the used part
var categoryRow = firstRowUsed.RowUsed();
// Move to the next row (it now has the titles)
categoryRow = categoryRow.RowBelow();
// Get all categories
while (!categoryRow.Cell(coCategoryId).IsEmpty())
{
String categoryName = categoryRow.Cell(coCategoryName).GetString();
categories.Add(categoryName);
categoryRow = categoryRow.RowBelow();
}

try the below code snippet, this will give the first row of a excel used range
Excel.Workbook xlWB = Globals.ThisAddIn.Application.ActiveWorkbook;
Excel.Worksheet xlWS = xlWB.ActiveSheet;
int firstRow = xlWS.UsedRange.Row;

copying of specific range of excel cells from one worksheet to another worksheet

I am writing a C# program which copies a range of cells from a worksheet of one workbook to a worksheet of an other workbook. But the problem I am facing is I am only able to copy and paste the whole worksheet of first workbook. I want to know how to select only a specific range(from row 5 [column 1 to column 10] to row 100 [column 1 to column 10]) and paste it in second workbook worksheet starting from row 2 column 8.
Also i want to know how a fill a column say from C1 to C100 with some value in a direct way instead of using the loop like below
for(i=1;i<2;i++)
{
for(j=1;j<101;i++)
{
worksheet.cells[i,j]="Fixed";
}
}
Here is the code that i have written so far
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using Excel = Microsoft.Office.Interop.Excel;
namespace ConsoleApplication3
{
class Program
{
static void Main(string[] args)
{
Excel.Application srcxlApp;
Excel.Workbook srcworkBook;
Excel.Worksheet srcworkSheet;
Excel.Range srcrange;
Excel.Application destxlApp;
Excel.Workbook destworkBook;
Excel.Worksheet destworkSheet;
Excel.Range destrange;
string srcPath;
string destPath;
//Opening of first worksheet and copying
srcPath="C:\\Documents and Settings\\HARRY\\Desktop\\incident.csv";
srcxlApp = new Excel.Application();
srcworkBook = srcxlApp.Workbooks.Open(srcPath);
srcworkSheet = srcworkBook.Worksheets.get_Item(1);
srcrange = srcworkSheet.UsedRange;
srcrange.Copy(Type.Missing);
//opening of the second worksheet and pasting
destPath = "C:\\Documents and Settings\\HARRY\\Desktop\\FIXED Aging incident Report.xls";
destxlApp = new Excel.Application();
destworkBook = destxlApp.Workbooks.Open(destPath,0,false);
destworkSheet = destworkBook.Worksheets.get_Item(1);
destrange = destworkSheet.Cells[1, 1];
destrange.Select();
destworkSheet.Paste(Type.Missing, Type.Missing);
destworkBook.SaveAs("C:\\Documents and Settings\\HARRY\\Desktop\\FIXED Aging incident Report " + DateTime.Now.ToString("MM_dd_yyyy") + ".xls");
srcxlApp.Application.DisplayAlerts = false;
destxlApp.Application.DisplayAlerts = false;
destworkBook.Close(true, null, null);
destxlApp.Quit();
srcworkBook.Close(false, null, null);
srcxlApp.Quit();
}
}
}

You should be able to do this:
Excel.Range from = srcworkSheet.Range("C1:C100");
Excel.Range to = destworkSheet.Range("C1:C100");
from.Copy(to);

mrtig has a very elegant solution. But it won't work if you have the workbooks in separate instances of excel. So, the key is to open them in just one instance. I've modified your example to show using this approach:
public void CopyRanges()
{
// only one instance of excel
Excel.Application excelApplication = new Excel.Application();
srcPath="C:\\Documents and Settings\\HARRY\\Desktop\\incident.csv";
Excel.Workbook srcworkBook = excelApplication.Workbooks.Open(srcPath);
Excel.Worksheet srcworkSheet = srcworkBook.Worksheets.get_Item(1);
destPath = "C:\\Documents and Settings\\HARRY\\Desktop\\FIXED Aging incident Report.xls";
Excel.Workbook destworkBook = excelApplication.Workbooks.Open(destPath,0,false);
Excel.Worksheet destworkSheet = destworkBook.Worksheets.get_Item(1);
Excel.Range from = srcworkSheet.Range("C1:C100");
Excel.Range to = destworkSheet.Range("C1:C100");
// if you use 2 instances of excel, this will not work
from.Copy(to);
destworkBook.SaveAs("C:\\Documents and Settings\\HARRY\\Desktop\\FIXED Aging incident Report " + DateTime.Now.ToString("MM_dd_yyyy") + ".xls");
srcxlApp.Application.DisplayAlerts = false;
destxlApp.Application.DisplayAlerts = false;
destworkBook.Close(true, null, null);
srcworkBook.Close(false, null, null);
excelApplication.Quit();
}

For the First part of setting the same value for the entire range, instead of looping following will work out
range1 = workSheet.get_Range("A1:B100");
range1.Value = "Fixed";
And for copying you can try what #mrtig has suggested.

creating excel sheet and writind data into it

I am working on writing the data into Excel sheet in c#.
I have wriiten the following code.
string excel_filename = #"C:\Users\Downloads\bookmain.xlsx";
Excel.Application excel = new Excel.Application();
excel.Visible = true;
Excel.Workbook wb = excel.Workbooks.Open(excel_filename);
Excel.Worksheet sh = wb.Sheets.Add();
sh.Name = "TestSheet";
sh.Cells[1, "A"].Value2 = "SNO";
sh.Cells[1, "B"].Value2 = "Name";
sh.Cells[1, "C"].Value2 = "ID";
for (int i = 0; i < 2; i++)
{
sh.Cells[i+2, "A"].Value2 = "1";
sh.Cells[i+2, "B"].Value2 = "A";
sh.Cells[i+2, "C"].Value2 = "1122";
}
wb.Save();
excel.Quit();
Here I have given the path of excel file that already exists and it is empty.
How to change this code that, when i give the path it should automatically check, if it exists it have to create otherwise no need to create.
Even my code also need to check sheet name, it it exist i shall directly edit it or else I need to create a new sheet.
Can any one share their response.
Thank you.

for checking existence of file :
if(!File.Exists(excel_filename))
{
//if not exists then only create:-
}
and for checking worksheet you can do like :
foreach (Sheet sheet in workbook.Sheets)
{
if (sheet.Name.equals("Test"))
{
//do something
}
}
UPDATED :
this is how it works :
Create Excel object
Excel.Application excel = new Excel.Application();
make Excel visible
excel.visible = true
add a worksheet
Excel.Worksheet sh = wb.Sheets.Add();
save it as
wb .SaveAs( #"C:\Users\Downloads\bookmain.xlsx",
Excel.XlFileFormat.xlXMLSpreadsheet, missing, missing,
false, false, Excel.XlSaveAsAccessMode.xlNoChange,
missing, missing, missing, missing, missing);

How to merge two Excel workbook into one workbook in C#?

Let us consider that I have two Excel files (Workbooks) in local. Each Excel workbook is having 3 worksheets.
Lets say WorkBook1 is having Sheet1, Sheet2, Sheet3
Workbook2 is having Sheet1, Sheet2, Sheet3.
So here I need to merge these two excel workbook into one and the new excel workbook that is let's say Workbook3 which will have total 6 worksheets (combination of workbook1 and workbook2).
I need the code that how to perform this operation in c# without using any third party tool. If the third party tool is free version then its fine.

An easier solution is to copy the worksheets themselves, and not their cells.
This method takes any number of excel file paths and copy them into a new file:
private static void MergeWorkbooks(string destinationFilePath, params string[] sourceFilePaths)
{
var app = new Application();
app.DisplayAlerts = false; // No prompt when overriding
// Create a new workbook (index=1) and open source workbooks (index=2,3,...)
Workbook destinationWb = app.Workbooks.Add();
foreach (var sourceFilePath in sourceFilePaths)
{
app.Workbooks.Add(sourceFilePath);
}
// Copy all worksheets
Worksheet after = destinationWb.Worksheets[1];
for (int wbIndex = app.Workbooks.Count; wbIndex >= 2; wbIndex--)
{
Workbook wb = app.Workbooks[wbIndex];
for (int wsIndex = wb.Worksheets.Count; wsIndex >= 1; wsIndex--)
{
Worksheet ws = wb.Worksheets[wsIndex];
ws.Copy(After: after);
}
}
// Close source documents before saving destination. Otherwise, save will fail
for (int wbIndex = 2; wbIndex <= app.Workbooks.Count; wbIndex++)
{
Workbook wb = app.Workbooks[wbIndex];
wb.Close();
}
// Delete default worksheet
after.Delete();
// Save new workbook
destinationWb.SaveAs(destinationFilePath);
destinationWb.Close();
app.Quit();
}
Edit: notice that you might want to Move method instead of Copy in case you have dependencies between the sheets, e.g. pivot table, charts, formulas, etc. Otherwise the data source will disconnect and any changes in one sheet won't effect the other.

Here's a working sample that joins two books into a new one, hope it will give you an idea:
using System;
using Excel = Microsoft.Office.Interop.Excel;
using System.Reflection;
namespace MergeWorkBooks
{
class Program
{
static void Main(string[] args)
{
Excel.Application app = new Excel.Application();
app.Visible = true;
app.Workbooks.Add("");
app.Workbooks.Add(#"c:\MyWork\WorkBook1.xls");
app.Workbooks.Add(#"c:\MyWork\WorkBook2.xls");
for (int i = 2; i <= app.Workbooks.Count; i++)
{
int count = app.Workbooks[i].Worksheets.Count;
app.Workbooks[i].Activate();
for (int j=1; j <= count; j++)
{
Excel._Worksheet ws = (Excel._Worksheet)app.Workbooks[i].Worksheets[j];
ws.Select(Type.Missing);
ws.Cells.Select();
Excel.Range sel = (Excel.Range)app.Selection;
sel.Copy(Type.Missing);
Excel._Worksheet sheet = (Excel._Worksheet)app.Workbooks[1].Worksheets.Add(
Type.Missing, Type.Missing, Type.Missing, Type.Missing
);
sheet.Paste(Type.Missing, Type.Missing);
}
}
}
}
}

You're looking for Office Autmation libraries in C#.
Here is a sample code to help you get started.

System.Data.Odbc.OdbcDataAdapter Odbcda;
//CSV File
strConnString = "Driver={Microsoft Text Driver (*.txt; *.csv)};Dbq=" + SourceLocation + ";Extensions=asc,csv,tab,txt;Persist Security Info=False";
sqlSelect = "select * from [" + filename + "]";
System.Data.Odbc.OdbcConnection conn = new System.Data.Odbc.OdbcConnection(strConnString.Trim());
conn.Open();
Odbcda = new System.Data.Odbc.OdbcDataAdapter(sqlSelect, conn);
Odbcda.Fill(ds, DataTable);
conn.Close();
This would read the contents of an excel file into a dataset.
Create multiple datasets like this and then do a merge.
Code taken directly from here.

How to add color to a cell in an excel sheet using C# COM Interop

I'm using C# COM Interop to create and update Excel files on the fly. I used the below code. But I'm not sure how to add color to a particular cell. Please help me with the same.
using Excel = Microsoft.Office.Interop.Excel;
Excel.Application excel = new Excel.Application();
excel.Visible = true;
Excel.Workbook wb = excel.Workbooks.Open(excel_filename);
Excel.Worksheet sh = wb.Sheets.Add();
sh.Name = "TestSheet";
sh.Cells[1, "A"].Value2 = "SNO";
sh.Cells[2, "B"].Value2 = "A";
sh.Cells[2, "C"].Value2 = "1122";
wb.Close(true);
excel.Quit();

Try this
wb.Cells[row, clmn].Interior.Color = System.Drawing.ColorTranslator.ToOle(System.Drawing.Color.Red)