Develop Reference

c# read specific columns from excel file

i have a tables like this
and i added checkboxs elements to form like this
i want to add the checkbox element text to datagridview then read the checked columns from excel file
if Date, Time, Price are checked datagridview will be like this
then get full Date column from excel file and add it to Date column in datagrid
my code to add checked boxes text as a columns in datagridview
DataTable dt = new DataTable();
foreach (Control checkbox in pnl.Controls)
if (checkbox.GetType() == typeof(CheckBox) && ((CheckBox) checkbox).Checked)
{
string txt = ((CheckBox)checkbox).Text;
dt.Columns.Add(new DataColumn(txt, typeof(object)));
}
datagrid.DataSource = dt;

There are a few steps which are needed before being able to grab data from an Excel file. So without your code, I don't know how much of this you have done. But here is the full explanation.
First
You have to add a reference to the Microsoft.Office.Interop.Excel dll (this assumes you aren't using epplus or another Nuget package). This link describes how to do this: How to reference Microsoft.Office.Interop.Excel dll?
Second
Include this library in whichever source file it is needed, and initialize an excel application (you'll also want InteropServices included):
using Microsoft.Office.Interop.Excel;
using System.Runtime.InteropServices;
// Global excel app object to be used anywhere
public Application ExcelApp;
// Intitializes an excel application by looking for an active one,
// and creating a new one if none are active
public void InitExcelApp()
{
try
{
ExcelApp = (Application)Marshal.GetActiveObject("Excel.Application")
}
catch(COMException ex)
{
ExcelApp = new Application
{
Visible = true
};
}
}
Third
You must initialize a workbook object. Here is how I do it, but my solution assumes you know the path to the desired Excel workbook:
Workbook myWorkbook = null;
// Checks open workbooks first
// Note that the path must be windows style. Ex: "C:\\Desktop\\myWorkbook.xlsx"
foreach (Workbook openWorkbook in ExcelApp.Workbooks)
{
if (openWorkbook.FullName == "<path to workbook>")
{
myWorkbook = openWorkbook;
}
}
// If no open workbooks were found at the known path, try opening one
if(myWorkbook is null)
{
myWorkbook = Excelapp.Workbooks.Open("<path to workbook>", Editable: true);
}
Fourth
Get the data you want. There are several ways to do this, and mine might not be the most efficient, but it works. In the code below I have included parameter names to hopefully make it more understandable.
// Gets the names of the checked items from the DataTable with columns you already added
// You could get these names from your checkboxes' names if you preferred
List<string> checkItems = new List<string>();
foreach (System.Data.DataColumn column in dt.Columns)
{
checkItems.Add(column.ColumnName);
}
// This dictionary holds info helpful for getting the correct data from excel:
// Key: a string containing the name of the column header, i.e. Date, Time, Price, etc.
// Value: an integer containing the number of that column in excel
Dictionary<string, int> excelColumnsInfo = new Dictionary<string, int>();
for (int columnNum = 1; columnNum <= myWorkbook.UsedRange.Columns.Count; columnNum++)
{
string columnHeader = myWorkbook.Cells[RowIndex: 1, ColumnIndex: columnNum].Value2.ToString();
if (checkedItems.Contains(columnHeader))
{
excelColumnsInfo.add(columnHeader, columnNum);
}
}
// Populates the data table with the data you need
// Start at row 2 to ignore the excel sheet's column headers
for (int rowNum = 2; rowNum <= myWorkbook.UsedRange.Rows.Count; rowNum++)
{
System.data.dataRow newRow = dt.NewRow();
foreach (KeyValuePair<string, int> columnInfo in excelColumnsInfo)
{
newRow[columnName: columnInfo.Key] = myWorkbook.Cells[RowIndex: rowNum, ColumnIndex: columnInfo.Value].Value2.ToString();
}
dt.Rows.Add(newRow);
}

Writing a excel using closed XML - adding custom column names

I need to write a list of objects to excel sheet as a table, in which each column represents object attributes or values. To the below method, Im passing column names in a separate List and data objects in a List, I managed to get the data displayed like below, but still I could not get the columns to display properly.
I referred the below documentation, but I could not find a way to get the titles display properly.
https://github.com/closedxml/closedxml/wiki/Inserting-Tables
Code
public string CreateExcelFile<T>(IEnumerable<T> list, string sheetName, string headerTitle, List<string> titles, string fileName, string savedPath)
{
var wb = new XLWorkbook();
var ws = wb.Worksheets.Add(sheetName);
ws.Cell(1, 1).Value = headerTitle; // sets excel sheet header
var rangeTitle = ws.Range(3, 1, 3, titles.Count); // range for row 3, column 1 to row 3, column titles.Count
rangeTitle.AddToNamed("Titles");
// Need to add columns names with in rangeTitle
//rangeTitle.InsertData(titles);
// write data from row 4 onwards
if (list != null && list.Any())
{
ws.Cell(4, 1).InsertData(list);
}
else
{
ws.Cell(4, 1).Value = "No data to show";
}
// styles
var titlesStyle = wb.Style;
titlesStyle.Font.Bold = true;
titlesStyle.Alignment.Horizontal = XLAlignmentHorizontalValues.Center;
titlesStyle.Fill.BackgroundColor = XLColor.Amber;
// style titles row
wb.NamedRanges.NamedRange("Titles").Ranges.Style = titlesStyle;
ws.Columns().AdjustToContents();
var filePath = savedPath + string.Format("{0}.xlsx", fileName);
wb.SaveAs(filePath);
return filePath;
}
Output excel
Output Im trying to get - I need to get values stored in titles in the Yellow highlighted row.
Can anyone help?

You could use InsertTable. The data is inserted as an Excel Table:
ws.Cell(1, 1).InsertTable(list.AsEnumerable());

I managed to get the columns to display by doing below.
// Need to add columns names with in rangeTitle
for (int i = 0; i < titles.Count; i++)
{
var columnNumber = i + 1;
ws.Cell(3, columnNumber).Value = titles[i];
}
This works for now. But, I wonder is there a better way to doing things (without manually assigning column names like above).

ws.Cell(3, 1).Value = new [] { titles };
If you set Value to an array, ClosedXML will write each object in the array to its own row, with one property of the object per column. (See https://github.com/ClosedXML/ClosedXML/wiki/Copying-IEnumerable-Collections)
In this case, the array we're passing in has only one object – an array of titles. That inner array gets written to the target row, and each item in the inner array gets written to a column in that row.

Populate DataGridView ComboBoxCell programmatically

I have a DataGridView in winforms, that contains a combobox column. The gridview is filled programmatically, and it is empty at start. "list" is a list containing custom objects. Value1/2/3 are unique to each row.
int[] array = new[] {value1,value2,value3}
for (int i = 0; i < list.Count; i++)
{
DataRow newrow = MyDataTable.NewRow();
newrow["idColumn"] = list[i].Customer_id;
newrow["dateoforderColumn"] = list[i].Customer_date;
newrow["commColumn"] = list[i].Customer_comment;
// This is what I want, and can't get to work.
newrow["comboColumn"] = array;
// I have also tried (newrow["comboColumn"] as DataGridViewComboColumn).DataSource
// but it didn't work either.
MyDataTable.Rows.Add(newrow);
}
How can I populate a freshly created combobox cell? Also, I need to do it within the for loop, because I need the index to get the data.

From the look of your code you just have one array of values that you need to set. In this case you only need to set it once for the column, not for every row, i usually do this in the constructor or before populating rows.
//Clear any junk items that may have been there from the designer or previous view
((DataGridViewComboBoxColumn)MyDataTable.Columns["comboColumn"]).Items.Clear();
//Add you new values
((DataGridViewComboBoxColumn)MyDataTable.Columns["comboColumn"]).Items.AddRange(array);
Then to set the value of the new row's cell
//Set value to be selected in new row
newrow["comboColumn"] = list[i].Customer_value;

DevExpress GridView | DataGridView

I want to do the following but using GridView of DevExpress , how Can I do that please ?
List<RCDATA_INDEX> somethings = new List<RCDATA_INDEX>();
foreach (DataGridViewRow row in (IEnumerable)this.dataGridView1.Rows)
{
AZ.RCDATA_INDEX items = new AZ.RCDATA_INDEX
{
datasize = Convert.ToUInt32(row.Cells[5].Value.ToString())
};
item.filenum = Convert.ToUInt32(row.Cells[2].Value.ToString()[7].ToString());
item.hash = row.Cells[1].Value.ToString();
item.realname = row.Cells[3].Value.ToString();
item.offset = Convert.ToUInt32(row.Cells[4].Value.ToString());
item.new_value = row.Cells[6].Value.ToString();
somethings.Add(items);
}

You can traverse through all the data rows within a GridView one-by-one, using the following approach:
// Obtain the number of data rows.
int dataRowCount = gridView.DataRowCount;
// Traverse data rows
for (int i = 0; i < dataRowCount; i++) {
object cellValue = gridView.GetRowCellValue(i, "... specify field name here ...");
// do something with cell Value
}
Please refer the Traversing Rows and Obtaining and Setting Cell Values help-articles to learn more;

I would prefer using BindingSource and bind it into Gridview. After that if you want to making manipulation of your data. You just need to call like this :
List<RCDATA_INDEX> somethings = new List<RCDATA_INDEX>();
var Result = RCDataBS.Cast<RCDATA_INDEX>();
somethings.AddRange(Result);
It would be much easier using this code and you don't need to spend your resource to convert all the data into your model.

How to get column name from gridview?

I would like to know how can I get a column name from a gridview? by its number not by name.
like : Name|Age|Birthday: ( so name=0 , age=1 etc...)
thanks.

You can get it like this :
gv.HeaderRow.Cells[i].Text
Or like this :
gv.Rows[0].Cells[i].Text
Rows[0] should be your header row.

//// Header column names
int gridViewCellCount = yourGridView.Rows[0].Cells.Count;
// string array to hold grid view column names.
string[] columnNames = new string[gridViewCellCount];
for (int i = 0; i < gridViewCellCount; i++)
{
columnNames[i] = ((System.Web.UI.WebControls.DataControlFieldCell)(yourGridView.Rows[0].Cells[i])).ContainingField.HeaderText;
}

simply
GridView1.Rows[0].Cells[0].Text;
try this if you want to all the cells value from each of the rows
foreach (GridViewRow r in GridView1.Rows)
{
string s = r.Cells[0].Text;
string y = r.Cells[1].Text;
}
update:
try this
foreach (TableCell Tc in GridView1.HeaderRow.Cells)
{
//if you are not getting value than find childcontrol of TabelCell.
string sssb = Tc.Text;
foreach (Control ctl in Tc.Controls)
{
//Child controls
Label lb = ctl as Label;
string s = lb.Text;
}
}

Revisiting this old question.... it's possible to get the field names of the data bound to a GridView with this kind of code. This makes a dictionary of colnum and field name.
private static IDictionary<int, string> GetGridViewFieldNames(object grid)
{
var names = new Dictionary<int, string>();
var view = grid as GridView;
if (view != null) {
for (var i = 0; i < view.Columns.Count; i++) {
var field = view.Columns[i] as BoundField;
if (field != null) {
names.Add(i, field.DataField);
}
}
}
return names;
}

This is not the answer to the question. It is only the answer if you never change the header text in the gridview. The asker of the question wanted to get the database field name by index.
I've seen a number of "answers" which only provide the text in the selected row of a gridview, or the header text which both do not answer the question that was asked...
You may ask why? If you were going to do audits of updates in a system and wanted to compare old values and new values and only update if they change and want to indicate which field was updated how do you show the database table field name at the index of the loop.
For instance:
Protected Sub gv_RowUpdating(sender As Object, e As System.Web.UI.WebControls.GridViewUpdateEventArgs)
Dim intValCount As Integer = Integer.Parse(e.NewValues.Count)
If intValCount > 0 Then
Dim i As Integer = 0
For i = 0 To intValCount - 1
If Not e.OldValues(i).Equals(e.NewValues(i)) Then
' values have changed, audit the change
Sys.Audits.General(intID, "the_database_table", <the table field by index(i)>, e.OldValues(i).ToString, e.NewValues(i).ToString)
End If
i += 1
Next
End If
End Sub
So the questions is how do you get the database table field name by index via code behind? I too have been searching for this and all the "answers" that I've seen are not the answers I think some of us are really looking for. All the mentioned methods I've seen here are not bullet proof references to a database tables field name.

Its easy: Here i read the gridview header text for each header cell and add them as new columns to a data table.
DataTable dt = new DataTable();
foreach(DataControlFieldHeaderCell column in yourGridview.HeaderRow.Cells)
{
dt.Columns.Add(column.Text.Trim().Replace(" ", ""));
}
//Make sure you do all this after yourGridview.DataBind();
//If you do not want to bind data first simply bind an empty list like so:
/* yourGridview.DataSource = new List<string>();
yourGridview.DataBind(); */