Simple Example of VSTO Excel using a worksheet as a datasource

Question

I think I'm running into a case of "the easiest answers are the hardest ones to find" and I haven't come across any searches that give this to me in a straightforward way. This is for Excel 2010 and VS 2010 within an existing VSTO (C#) project.

I have an Excel worksheet that contains 4 columns of data that I would like to use as a source for a DataGridView. Can someone please provide C# code snippets for (1) getting the data from a particular worksheet and populating a custom object with it? (2) binding the object (like an IEnumerable list) to a Datagridview and (3) some snippets for the update and delete functionality that would be inherent to the grid and feed back to the source worksheet.

I know I'm asking for a lot here, but so much of the VSTO information seems to be dis-jointed and not always easy to find. Thanks!

Answer 1

Edit: Great, I just noticed that I missed a big part of your question, getting updates and deletes back to the worksheet. I have absolutely no idea if that is possible but I think that makes my solution worthless. I'll leave it here anyway, maybe it can help in any way.

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Why do you need VSTO? As far as I know VSTO is used for Office Add-Ins. But since you want to show the data in a DataGridView I assume that you have a WinForms application that should just access a workbook. In this case you can simply open the workbook by using Office Interop. Just add a reference to Microsoft.Office.Interop.Excel to your project and add a using Microsoft.Office.Interop.Excel; statement.

MSDN reference documentation for Excel Interop can be found here: http://msdn.microsoft.com/en-us/library/ms262200%28v=office.14%29.aspx

I'll give you the Excel part, maybe someone else can do the rest.

First, open Excel and the workbook:

Application app = new Application();
// Optional, but recommended if the user shouldn't see Excel.
app.Visible = false;
app.ScreenUpdating = false;
// AddToMru parameter is optional, but recommended in automation scenarios.
Workbook workbook = app.Workbooks.Open(filepath, AddToMru: false);

Then somehow get the correct worksheet. You have a few possiblities:

// Active sheet (should be the one which was active the last time the workbook was saved).
Worksheet sheet = workbook.ActiveSheet;
// First sheet (notice that the first is actually 1 and not 0).
Worksheet sheet = workbook.Worksheets[1];
// Specific sheet.
// Caution: Default sheet names differ for different localized versions of Excel.
Worksheet sheet = workbook.Worksheets["Sheet1"];

Then get the correct range. You didn't specify how you know where the needed data is, so I'll assume it is in fixed columns.

// If you also know the row count.
Range range = sheet.Range["A1", "D20"];
// If you want to get all rows until the last one that has some data.
Range lastUsedCell = sheet.Cells.SpecialCells(XlCellType.xlCellTypeLastCell);
string columnName = "D" + lastUsedCell.Row;
Range range = sheet.Range["A1", columnName];

Get the values:

// Possible types of the return value:
// If a single cell is in the range: Different types depending on the cell content
// (string, DateTime, double, ...)
// If multiple cells are in the range: Two dimensional array that exactly represents
// the range from Excel and also has different types in its elements depending on the
// value of the Excel cell (should always be that one in your case)
object[,] values = range.Value;

That two dimensional object array can then be used as a data source for your DataGridView. I haven't used WinForms for years so I don't know if you can bind it directly or first need to get the data into some specific format.

Finally close Excel again:

workbook.Close(SaveChanges: false);
workbook = null;
app.Quit();
app = null;
// Yes, we really want to call those two methods twice to make sure all
// COM objects AND all RCWs are collected.
GC.Collect();
GC.WaitForPendingFinalizers();
GC.Collect();
GC.WaitForPendingFinalizers();

Correctly closing Excel after using Interop is a task itself because you have to make sure that all references to COM objects have been released. The easiest way I have found to do this is to do all the work except opening and closing Excel and the workbook (so my first and last code block) in a seperate method. This ensures that all COM objects used in that method are out of scope when Quit is called.