Re: How to make a dll library? - C# Discussion Boards

16-Nov-20 0:22

I have wrote some lines of code for exporting DataGridView contents to Excel file. The code works fine in the main Form. I want to make a class (.dll file) from my code so I could use it as reference in many projects. How is it possible?
My code is:

private void btnExport_Click(object sender, EventArgs e)
       {
           Microsoft.Office.Interop.Excel._Application app = new Microsoft.Office.Interop.Excel.Application();
           Microsoft.Office.Interop.Excel._Workbook workbook = app.Workbooks.Add(Type.Missing);
           Microsoft.Office.Interop.Excel._Worksheet worksheet = null;
           worksheet = workbook.Sheets["Sheet1"];
           worksheet = workbook.ActiveSheet;
           worksheet.Name = "pmInfo";
           for (int i = 1; i < dataGridView1.Columns.Count+1; i++)
           {
               worksheet.Cells[1, i] = dataGridView1.Columns[i - 1].HeaderText;
           }
           for (int i = 0; i < dataGridView1.Rows.Count; i++)
           {
               for (int j = 0; j < dataGridView1.Columns.Count; j++)
               {
                   worksheet.Cells[i + 2, j + 1] = dataGridView1.Rows[i].Cells[j].Value.ToString();
               }
           }
           var saveFileDialoge = new SaveFileDialog();
           saveFileDialoge.FileName = "Output";
           saveFileDialoge.DefaultExt = ".xlsx";
           if (saveFileDialoge.ShowDialog()==DialogResult.OK)
           {
               workbook.SaveAs(saveFileDialoge.FileName, Type.Missing, Type.Missing, Type.Missing, Type.Missing, Type.Missing, Microsoft.Office.Interop.Excel.XlSaveAsAccessMode.xlExclusive, Type.Missing, Type.Missing, Type.Missing, Type.Missing, Type.Missing);

           }
       }

Create a .NET Standard class library using Visual Studio - .NET Core | Microsoft Docs[^]

Richard MacCutchan16-Nov-20 0:44

Richard MacCutchan

16-Nov-20 0:44

Alex Dunlop16-Nov-20 0:47

16-Nov-20 0:47

I pasted this code in the Class, but "Columns" and "Rows" have red underline. I cannot compile the class.

Richard MacCutchan16-Nov-20 0:51

Richard MacCutchan

16-Nov-20 0:51

There is quite a bit missing from that code to make it into a dll. I suggest you follow the link I gave you and read up on how to make a class library.

OriginalGriff16-Nov-20 0:50

16-Nov-20 0:50

First, make it as generic as possible: instead of writing it as an Event handler which works with a specific DataGridView and Sheet make it a generic routine that takes several parameters: The data source, the Sheet name, and the file path to write to. You call that generic method from your handler.
Ideally, you shouldn't pass a control like a DGV, but the underlying datasource it uses instead. You can access the properties from that quite easily - this shows you how: Converting a List to a DataTable[^]

You should not be using a dialog in a dll, as there is no guarantee that the calling application will be running under windows - it potentially could be a web app or on a server, where the user can't see a SaveFileDialog, and shouldn't have access to the file system anyway.

Then create a new Project as a ClassLibrary and move your method into it.
Add a reference (and using statement if necessary) to the library to your original project, and you can call it from there.

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Alex Dunlop16-Nov-20 1:51

16-Nov-20 1:51

I tried the following class code. Now, my problem is that "Rows" and "Columns" have red underline. They have not been defined in my class while I have used Microsoft Office Excel 16 object reference.
How can I sole those red underlines?
My updated code:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace DataGridView
{
    class ExcelExport
    {

        public void Export(string fileName, string DataSource,string FileName)
        {
            /*fileName is the name of the file will be written.
            DataSource is the DataGridView name used*/
            Microsoft.Office.Interop.Excel._Application app = new Microsoft.Office.Interop.Excel.Application();
            Microsoft.Office.Interop.Excel._Workbook workbook = app.Workbooks.Add(Type.Missing);
            Microsoft.Office.Interop.Excel._Worksheet worksheet = null;
            worksheet = workbook.Sheets["Sheet1"];
            worksheet = workbook.ActiveSheet;
            worksheet.Name = fileName;
            for (int i = 1; i < DataSource.Columns.Count + 1; i++)
            {
                worksheet.Cells[1, i] = DataSource.Columns[i - 1].HeaderText;
            }
            for (int i = 0; i < DataSource.Rows.Count; i++)
            {
                for (int j = 0; j < DataSource.Columns.Count; j++)
                {
                    worksheet.Cells[i + 2, j + 1] = DataSource.Rows[i].Cells[j].Value.ToString();
                }
            }
            var saveFileDialoge = new SaveFileDialog();
            saveFileDialoge.FileName = FileName;
            saveFileDialoge.DefaultExt = ".xlsx";
            if (saveFileDialoge.ShowDialog() == DialogResult.OK)
            {
                workbook.SaveAs(saveFileDialoge.FileName, Type.Missing, Type.Missing, Type.Missing, Type.Missing, Type.Missing, Microsoft.Office.Interop.Excel.XlSaveAsAccessMode.xlExclusive, Type.Missing, Type.Missing, Type.Missing, Type.Missing, Type.Missing);

            }
        }
    }
}

OriginalGriff16-Nov-20 2:17

16-Nov-20 2:17

Look at your code:

public void Export(string fileName, string DataSource,string FileName)
        {
            /*fileName is the name of the file will be written.
            DataSource is the DataGridView name used*/
...
            for (int i = 1; i < DataSource.Columns.Count + 1; i++)

Why do you think that a string would have rows or columns?

Alex Dunlop16-Nov-20 2:25

16-Nov-20 2:25

Yes, I notice my fault later. But I tried to create an DGV object like this:

private DataGridView DataSource = new DataGridView();

But it shows red underline under DataGridView. It says, DataGridView is a namespace.

OriginalGriff16-Nov-20 2:41

16-Nov-20 2:41

Why are you trying to create a DataGridView at all? Do you expect magic to happen and it to be filled with data that exists in a different DataGridView?

Why do I get the feeling that you have no idea what you are doing, and are so far out of your depth that you are just guessing what to try? You didn't write that Excel code at all, did you?

Alex Dunlop16-Nov-20 2:48

16-Nov-20 2:48

It was a tutorial. Please help me. What should I do?

OriginalGriff16-Nov-20 2:50

16-Nov-20 2:50

Pass the actual DataGridView - or better the DataSource it was loaded from - and use that.

Alex Dunlop16-Nov-20 3:09

16-Nov-20 3:09

Can you write it in a line of code? Please

OriginalGriff16-Nov-20 3:40

16-Nov-20 3:40

You are kidding, right?
You don't know how to pass a parameter?

myMethod(datatGridView1);

As far as using the data source instead goes, I have no idea how you are filling your DGV - but I suspect you don't either ... Sigh | :sigh:

Alex Dunlop16-Nov-20 4:15

16-Nov-20 4:15

datatGridView1 has not defined in Class view. There is no link between my main project and the class for datatGridView1.

OriginalGriff16-Nov-20 4:37

16-Nov-20 4:37

We are going to be here all day, I suspect ...

You have a DGV in one form.
It contains data which it is displaying.
That data is organised into rows and columns.
Somewhere in your code, you added data to that DGV, be it by creating individual columns and then adding rows, or by creating a DataTable / Collection which held the data and setting that as the DataSource for the DGV.

You want to use the data in the DGV in a separate method (in a separate Assembly which is a DLL) so that it can output data to an XLSX file.

That means you have to pass the DGV or it's source data to the method in some way via a parameter, or the method has no way to access it and no idea what to write to the file.

Are you with me so far?

Message Closed

16-Nov-20 5:23

16-Nov-20 5:23

Message Closed

modified 17-Nov-20 1:59am.

OriginalGriff16-Nov-20 5:41

16-Nov-20 5:41

Excellent.
First off, change the way you fill your DGV. Instead of adding columns and rows directly, create a DataTable instance instead, populate that, adn set that as the DataSource property of the DGV.

The DGV will now display the data and update it as you add items to the underlying DataTable.

When you want to output the data to XLSX, pass the DataTable instance to your method:

private DataTable theSource = new DataTable();
private void FrmMain_Shown(object sender, EventArgs e)
    {
    theSource.Columns.Add("Column 1");
    theSource.Columns.Add("Column 2");
    theSource.Rows.Add("cccc1111", 666);
    myDataGridView.DataSource = theSource;
    }
private void AddButton_Click(object sender, EventArgs e)
    {
    theSource.Rows.Add(DateTime.Now, "hello");
    }

private void OutputButton_Click(object sender, EventArgs e)
    {
    MyDLLAssemblyClass.OutputToXLSX(theSource, @"d:\Test Data\myFile.xslx");
    }

private static void OutputToXLSX(DataTable dt, string outputPath)
    {
    ...
    }

You can then just add a using line for System.Data to your DLL assembly class and use the Row and Column from the DataTable.

Now your DLL file doesn't need to know what the heck the rest of your code is doing, it just wants a DataTable with the data to output.

OriginalGriff16-Nov-20 2:21