Freeze Panes in OpenXml SDK 2.0 for Excel document

I was trying to solve the same problem and ended up opening the Open XML SDK 2.0 Productivity Tool and using the Compare Files... feature to compare two spreadsheets, one with frozen panes and one without.

When I did that, I was led to code that looked basically like this:

WorkbookPart wbp = doc.WorkbookPart;
WorksheetPart wsp = wbp.WorksheetParts.First();

SheetViews sheetviews = wsp.Worksheet.GetFirstChild<SheetViews>();
SheetView sv = sheetviews.GetFirstChild<SheetView>();
Selection selection = sv.GetFirstChild<Selection>();
Pane pane = new Pane(){ VerticalSplit = 1D, TopLeftCell = "A2", ActivePane = PaneValues.BottomLeft, State = PaneStateValues.Frozen };
sv.InsertBefore(pane,selection);
selection.Pane = PaneValues.BottomLeft;

I added this to my program and it seemed to do the trick.

You can add the Selection as well:

WorkbookPart wbp = doc.WorkbookPart;
WorksheetPart wsp = wbp.WorksheetParts.First(); 

SheetViews sheetViews = wsp.Worksheet.GetFirstChild<SheetViews>();
SheetView sheetView = sheetViews.GetFirstChild<SheetView>();

Selection selection1 = new Selection() { Pane = PaneValues.BottomLeft };

Pane pane1 = new Pane() { VerticalSplit = 1D, TopLeftCell = "A2", ActivePane = PaneValues.BottomLeft, State = PaneStateValues.Frozen };

sheetView.Append(pane1);
sheetView.Append(selection1);

When I used the code provided in the other answers, I kept receiving a null error for the SheetViews. I used the SDK Productivity Tools to view the code for an excel document with a frozen pane, which helped me create the below code. Instead of using the GetFirstChild method, I had to create new instances of the SheetViews and SheetView classes and append them.

Here is the code.

WorkbookPart workbookPart = document.AddWorkbookPart();
workbookPart.Workbook = new Workbook();

WorksheetPart worksheetPart = workbookPart.AddNewPart<WorksheetPart>();
worksheetPart.Worksheet = new Worksheet();

SheetViews sheetViews = new SheetViews();
SheetView sheetView = new SheetView() { TabSelected = true, WorkbookViewId = (UInt32Value)0U };
Pane pane = new Pane() { ActivePane = PaneValues.BottomLeft, State = PaneStateValues.Frozen, TopLeftCell = "A2", VerticalSplit = 1D };
Selection selection = new Selection() { Pane = PaneValues.BottomLeft };
sheetView.Append(pane);
sheetView.Append(selection);
sheetViews.Append(sheetView);
worksheetPart.Worksheet.Append(sheetViews);

One extra note is that when creating the SheetView, you must include the TabSelected and WorkbookViewId values, otherwise you will receive an error when opening the file about "We found a problem with some content in...."

Also, for anyone who wants to freeze the first column, instead of the first row, here is an example.

var sheetViews = new SheetViews();
var sheetView = new SheetView() { TabSelected = true, WorkbookViewId = (UInt32Value)0U };
var pane = new Pane() { ActivePane = PaneValues.TopRight, HorizontalSplit = 1D, State = PaneStateValues.Frozen, TopLeftCell = "B1" };
var selection = new Selection() { Pane = PaneValues.TopRight };
sheetView.Append(pane);
sheetView.Append(selection);
sheetViews.Append(sheetView);