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How could I speed up deleting columns in Excel?

I would like to accelerate the process of deleting columns in Excel. I have 2 Excel files. Let's say data file where all data exist and the deleting column names in other file. There are many worksheets in data file some have more than 15000 columns and around 2500 rows in deleting column file. It is taking longer time to delete. My question how could I speed up the code below?
private void workerdelete_DoWork(object sender, System.ComponentModel.DoWorkEventArgs e)
{
try
{
totalRow = xlWorksheetdelvariable.UsedRange.Rows.Count;
Excel.Range startCell = xlWorksheetdelvariable.Cells[2, 1];
Excel.Range endCell = xlWorksheetdelvariable.Cells[totalRow, 1];
Excel.Range currentRange = xlWorksheetdelvariable.get_Range(startCell, endCell).Cells;
object[,] matrixReaddelvariable = (object[,])currentRange.Value;
foreach (Excel.Worksheet sheet in xlWorkbookDelete.Sheets)
{
xlWorksheetdelete = xlWorkbookDelete.Sheets[sheet.Index];
columnCount = xlWorksheetdelete.UsedRange.Columns.Count;
int rowCount = xlWorksheetdelete.UsedRange.Rows.Count;
Excel.Range startCelldelete = xlWorksheetdelete.Cells[1, 1];
Excel.Range endCelldelete = xlWorksheetdelete.Cells[1, columnCount];
Excel.Range currentRangedelete = xlWorksheetdelete.get_Range(startCelldelete, endCelldelete).Cells;
object[,] matrixReaddelete = (object[,])currentRangedelete.Value;
List<int> delCols = new List<int>();
for (int c = 1; c <= columnCount; c++)
{
for (int r = 1; r < totalRow; r++)
{
if (dellabel == true)
{
if (matrixReaddelete[1, c].ToString() == matrixReaddelvariable[r, 1].ToString()||matrixReaddelete[1, c].ToString().Contains("_label"))
{
delCols.Insert(0, c);
break;
}
}
else if(matrixReaddelete[1, c].ToString() == matrixReaddelvariable[r, 1].ToString())
{
delCols.Insert(0, c);
break;
}
}
int percentage = (c + 1) * 50 / columnCount;
workerdelete.ReportProgress(percentage);
}
foreach (int colIndex in delCols)
{
xlWorksheetdelete.Columns[colIndex].Delete();
int percentage = 50 + ( delCols.IndexOf(colIndex) + 1 ) * 50 / delCols.Count;
workerdelete.ReportProgress(percentage);
}
}
}
catch (Exception ex)
{
System.Windows.MessageBox.Show(ex.Message);
}
}

How to Check for Empty data entry before populating ListBox

private void LoadExcelSheet(string path, int sheet){
_Application excel = new Excel.Application();
Workbook wb;
Worksheet ws;
string data = "";
int row = 0;
int col = 0;
wb = excel.Workbooks.Open(path);
ws = wb.Worksheets[sheet];
listBox1.Items.Clear();
for (row = 1; row < 10; row++){
data = " ";
for (col = 1; col < 3; col++) {
data += ws.Cells[row, col].Value2 + " ";
}
//wanted to filter out empty cells/data and at the same time count
//number of items in the list... row should stop.. I think!
if(data == null){
break;
}
listBox1.Items.Add(data);
}
The if statement doesn't seems to work no matter what I do. I would appreciate it very if anyone could point me in the right direction.

use it like this:
if (data.Trim().Length < 1)
{
return;
}
use return not break

Add a condition like this
If(string.IsNullOrEmpty(data))
{
Break;
}

Most efficient way of converting a DataTable to CSV

I'm working with DataTable's and I need to convert them to a CSV file format. Most of the tables I am working with have over 50,000 records so I'm trying to minimize the time it takes to convert them.
Here is my current method:
public static string table_to_csv(DataTable table)
{
string file = "";
foreach (DataColumn col in table.Columns)
file = string.Concat(file, col.ColumnName, ",");
file = file.Remove(file.LastIndexOf(','), 1);
file = string.Concat(file, "\r\n");
foreach (DataRow row in table.Rows)
{
foreach (object item in row.ItemArray)
file = string.Concat(file, item.ToString(), ",");
file = file.Remove(file.LastIndexOf(','), 1);
file = string.Concat(file, "\r\n");
}
return file;
}
Is there any way I can improve the efficiency of this method? I'm welcome to any modifications and ideas that you have!

Use a System.Text.StringBuilder for huge strings - that's pretty fast.
I implemented this one:
public static string DataTableToCSV(this DataTable datatable, char seperator)
{
StringBuilder sb = new StringBuilder();
for (int i = 0; i < datatable.Columns.Count; i++)
{
sb.Append(datatable.Columns[i]);
if (i < datatable.Columns.Count - 1)
sb.Append(seperator);
}
sb.AppendLine();
foreach (DataRow dr in datatable.Rows)
{
for (int i = 0; i < datatable.Columns.Count; i++)
{
sb.Append(dr[i].ToString());
if (i < datatable.Columns.Count - 1)
sb.Append(seperator);
}
sb.AppendLine();
}
return sb.ToString();
}

Here's a method I have in my Utility class. Works well for what I'm doing.
public static void GenerateCSV(DataTable dt)
{
StringBuilder sb = new StringBuilder();
try
{
int count = 1;
int totalColumns = dt.Columns.Count;
foreach (DataColumn dr in dt.Columns)
{
sb.Append(dr.ColumnName);
if (count != totalColumns)
{
sb.Append(",");
}
count++;
}
sb.AppendLine();
string value = String.Empty;
foreach (DataRow dr in dt.Rows)
{
for (int x = 0; x < totalColumns; x++)
{
value = dr[x].ToString();
if (value.Contains(",") || value.Contains("\""))
{
value = '"' + value.Replace("\"", "\"\"") + '"';
}
sb.Append(value);
if (x != (totalColumns - 1))
{
sb.Append(",");
}
}
sb.AppendLine();
}
}
catch (Exception ex)
{
// Do something
}
}

I have used this method which copies object array to an Excel cell range rather than copying row by row and then column by column & it proved to be quite efficient way
public void ExportToExcel(DataTable dataTable, String pathToSave)
{
// Create the Excel Application object
var excelApp = new ApplicationClass();
// Create a new Excel Workbook
Workbook excelWorkbook = excelApp.Workbooks.Add(Type.Missing);
int sheetIndex = 0;
// Copy the DataTable to an object array
var rawData = new object[dataTable.Rows.Count + 1, dataTable.Columns.Count];
// Copy the column names to the first row of the object array
for (var col = 0; col < dataTable.Columns.Count; col++)
{
rawData[0, col] = dataTable.Columns[col].ColumnName;
}
// Copy the values to the object array
for (var col = 0; col < dataTable.Columns.Count; col++)
{
for (int row = 0; row < dataTable.Rows.Count; row++)
{
rawData[row + 1, col] = dataTable.Rows[row].ItemArray[col];
}
}
// Calculate the final column letter
string finalColLetter = string.Empty;
const string colCharset = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
int colCharsetLen = colCharset.Length;
if (dataTable.Columns.Count > colCharsetLen)
{
finalColLetter = colCharset.Substring(
(dataTable.Columns.Count - 1) / colCharsetLen - 1, 1);
}
finalColLetter += colCharset.Substring((dataTable.Columns.Count - 1) % colCharsetLen, 1);
// Create a new Sheet
var excelSheet = (Worksheet)excelWorkbook.Sheets.Add(excelWorkbook.Sheets.Item[++sheetIndex], Type.Missing, 1, XlSheetType.xlWorksheet);
excelSheet.Name = dataTable.TableName;
// Fast data export to Excel
var excelRange = string.Format("A1:{0}{1}", finalColLetter, dataTable.Rows.Count + 1);
excelSheet.Range[excelRange, Type.Missing].Value2 = rawData;
// Mark the first row as BOLD and BLUE
var headerColumnRange = (Range)excelSheet.Rows[1, Type.Missing];
headerColumnRange.Font.Bold = true;
headerColumnRange.Font.Color = 0xFF0000;
headerColumnRange.EntireColumn.AutoFit();
// Save and Close the Workbook
excelWorkbook.SaveAs(pathToSave, XlFileFormat.xlWorkbookNormal, Type.Missing,
Type.Missing, Type.Missing, Type.Missing, XlSaveAsAccessMode.xlExclusive,
Type.Missing, Type.Missing, Type.Missing, Type.Missing, Type.Missing);
excelWorkbook.Close(true, Type.Missing, Type.Missing);
excelWorkbook = null;
// Release the Application object
excelApp.Quit();
excelApp = null;
// Collect the unreferenced objects
GC.Collect();
GC.WaitForPendingFinalizers();
}

Export Sql data to Excel , Store long int to string in excel

I have this working C# code to export Sql Server data to excel. The problem is one column contains long int and it appears in excel as 6.71524E+11. So I understand that we have to convert it as string in excel.
How to implement that in my code? Examples would be appreciated.
public static void ExportToExcel(DataTable dt)
{
try
{
string conString = "Data Source=DELL\\SQLSERVER1;Trusted_Connection=True;DATABASE=Camo;CONNECTION RESET=FALSE";
SqlConnection sqlCon = new SqlConnection(conString);
sqlCon.Open();
SqlDataAdapter da = new SqlDataAdapter("select TOP 10000 LocalSKU,ItemName, QOH,Price,Discontinued,Barcode,Integer2,Integer3,SalePrice,SaleOn,Price2 from dbo.Inventory", sqlCon);
System.Data.DataTable dtMainSQLData = new System.Data.DataTable();
da.Fill(dtMainSQLData);
DataColumnCollection dcCollection = dtMainSQLData.Columns;
// Export Data into EXCEL Sheet
Microsoft.Office.Interop.Excel.ApplicationClass ExcelApp = new Microsoft.Office.Interop.Excel.ApplicationClass();
ExcelApp.Application.Workbooks.Add(Type.Missing);
int i = 1;
int j = 1;
//header row
foreach (DataColumn col in dtMainSQLData.Columns)
{
ExcelApp.Cells[i, j] = col.ColumnName;
j++;
}
i++;
//data rows
foreach (DataRow row in dtMainSQLData.Rows)
{
for (int k = 1; k < dtMainSQLData.Columns.Count + 1; k++)
{
ExcelApp.Cells[i, k] = row[k - 1].ToString();
}
i++;
}
ExcelApp.ActiveWorkbook.SaveCopyAs("C:/Users/Administrator.CAMO/Downloads/FtpFilesStorage/Export/Sheet1.xlsx");
ExcelApp.ActiveWorkbook.Saved = true;
ExcelApp.Quit();
Console.WriteLine(".xlsx file Exported succssessfully.");
}

This method work for exporting to an Excel file.
private void ExportToExcel(DataTable Tbl, string ExcelFilePath = null)
{
try
{
if (Tbl == null || Tbl.Columns.Count == 0)
throw new Exception("ExportToExcel: Null or empty input table!\n");
// load excel, and create a new workbook
Excel.Application excelApp = new Excel.Application();
//Excel.Workbook ExcelBookServices = excelApp.Workbooks.Add();
excelApp.Workbooks.Add();
// single worksheet
Excel._Worksheet workSheet = (Excel._Worksheet)excelApp.ActiveSheet;
// column headings
for (int i = 0; i < Tbl.Columns.Count; i++)
{
workSheet.Cells[1, (i + 1)] = Tbl.Columns[i].ColumnName;
}
// rows
for (int i = 0; i < Tbl.Rows.Count; i++)
{
// to do: format datetime values before printing
for (int j = 0; j < Tbl.Columns.Count; j++)
{
workSheet.Cells[(i + 2), (j + 1)] = Tbl.Rows[i][j];
}
}
workSheet.Columns.AutoFit();
//workSheet.Columns.Style = "Output";
//Excel.Range cell = ((Excel.Range)workSheet.Cells[Tbl.Rows.Count, Tbl.Columns.Count]);
// check fielpath
if (ExcelFilePath != null && ExcelFilePath != "")
{
try
{
workSheet.SaveAs(ExcelFilePath);
excelApp.Quit();
//File Saved Message
}
catch (Exception ex)
{
//ExportToExcel: Excel file could not be saved! Check filepath Message
}
}
else // no filepath is given
{
excelApp.Visible = true;
}
}
catch (Exception ex)
{
//Error in creating the Excel file
ScriptManager.RegisterStartupScript(this, GetType(), "Message", "ExportToExcel: \n" + ex.Message, true);
}
}

Change the for loop to
int i = 1;
int j = 1;
//header row
foreach (DataColumn col in dtMainSQLData.Columns)
{
ExcelApp.Cells[i, j] = col.ColumnName;
j++;
ExcelApp.Rows.AutoFit();
ExcelApp.Columns.AutoFit();
}
i++;
Console.Write("Progressing......65% \n Wait for around 8 minutes \r");
//data rows
foreach (DataRow row in dtMainSQLData.Rows)
{
for (int k = 1; k < dtMainSQLData.Columns.Count + 1; k++)
{
ExcelApp.Cells[i, k] = "'" + row[k - 1].ToString();
}
i++;
ExcelApp.Columns.AutoFit();
ExcelApp.Rows.AutoFit();
}

use the property NumberFormat:
MyWorkBook.NumberFormat = "#";

How to solve Unable to cast object of type 'System.Data.DataView' to type 'System.Data.DataTable' ERROR

i have Devxpress GridControl on the form,
and i want to send data on this grid to excel.
and i dont want to do this with ExportToExcel method
i have googled and found this code
but this code is for DataGrid control of .Net
and it gives an error when it tries to convert
DevExpress.XtraGrid.Views.Grid.GridView to System.Data.DataView
here is the code
public string LastCoulmLetter(int coulmnCount)
{
string finalColLetter = string.Empty;
string colCharset = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
int colCharsetLen = colCharset.Length;
if (coulmnCount > colCharsetLen)
{
finalColLetter = colCharset.Substring(
(coulmnCount - 1) / colCharsetLen - 1, 1);
}
finalColLetter += colCharset.Substring(
(coulmnCount - 1) % colCharsetLen, 1);
return finalColLetter;
}
public void FromGridToExcel()
{
if (gridView1.RowCount <= 0)
return;
Excel.Application xls = new Excel.Application();
Excel.Workbook wb;
Excel.Worksheet sheet;
object SalakObje = System.Reflection.Missing.Value;
wb = xls.Workbooks.Add(SalakObje);
sheet = (Excel.Worksheet)wb.ActiveSheet;
sheet.Name = "Result";
xls.Visible = true;
DataTable dt = (DataTable)gridView1.DataSource; // Error comes in here
// Copy the DataTable to an object array
object[,] rawData = new object[dt.Rows.Count + 1, dt.Columns.Count];
// Copy the column names to the first row of the object array
for (int col = 0; col < dt.Columns.Count; col++)
{
rawData[0, col] = dt.Columns[col].ColumnName;
}
// Copy the values to the object array
for (int col = 0; col < dt.Columns.Count; col++)
{
for (int row = 0; row < dt.Rows.Count; row++)
{
rawData[row + 1, col] = dt.Rows[row].ItemArray[col];
}
}
// Fast data export to Excel
string excelRange = string.Format("A1:{0}{1}",LastCoulmLetter(dt.Columns.Count), dt.Rows.Count + 1);
sheet.get_Range(excelRange, Type.Missing).Value2 = rawData;
sheet.get_Range(excelRange).Columns.AutoFit();
}
So what is the problem and how to fix it

The problem appears to be that your DataSource is a DataView, not a DataTable.
Some options:
Cast it to a DataView if you want to use the same filters:
DataView dv = (DataView)gridView1.DataSource;
Use the .Table property to get the source table if you want the raw data:
DataTable dt = ((DataView)gridView1.DataSource).Table;

Try this instead:
DataTable dt = ((DataView)gridView1.DataSource).Table;