Strange behaviour of TableCell blocks

Question

Brief background
I'm trying to write a method that splits a table cell but I'm trying to write it in a generic way such that the content Blocks of the created cells can come from any source, including the BlockCollection from the original cell.

I was keeping the existing cell as the first in the set of new cells, which means I want to clear its contents before adding the new contents.
If I do this and the contents is coming from the original cell (through the generic method) then those contents will be lost.

So what I needed to do was check if the collection of Blocks I am adding is the original BlockCollection and leave it alone but it was getting cleared.

This is where I tracked the bug to. A simple test illustrates:

[TestMethod]
public void TestBlockReference()
{
    TableCell cell = new TableCell(new Paragraph(new Run("test")));
    TableRow row = new TableRow();
    row.Cells.Add(cell);

    Assert.IsTrue(IsCellsBlocks(cell, cell.Blocks));
}

static bool IsCellsBlocks(TableCell cell, BlockCollection bc)
{
    return bc == cell.Blocks;
}

This fails!

I got around this by not keeping the original cell but I still would like to know why that equality check fails. Is == overidden to always return false? If so why?

Answer 1

That seems like a bug, I would report it as such and see what the response is.

https://connect.microsoft.com/

---

John Fenton

Answer 2

-> I got around this by not keeping the original cell but I still would like to know why that equality check fails. Is == overidden to always return false? If so why?

It seems this is the desired behaviour, the following is the implementation of the Blocks property:

/// <value>
/// Collection of Blocks contained in this Section.
/// </value>
[DesignerSerializationVisibility(DesignerSerializationVisibility.Content)]
public BlockCollection Blocks
{
    get
    {
        return new BlockCollection(this, /*isOwnerParent*/true);
    }
}

So every time you access the Blocks property, and new instance of BlockCollection will be returned.

Hope this helps

Answer 3

Interesting... wonder why they decided to do it that way.  (They probably had a good reason... just curious as to what it was.)

Paragraph p = new Paragraph(new Run("test"));

TableCell cell = new TableCell(p);

TableCell cell2 = new TableCell(p);

cell.Blocks.FirstBlock == cell.Blocks.FirstBlock    // Returns True
cell.Blocks.FirstBlock == cell2.Blocks.FirstBlock  // Returns False

Does seem to work so the OP could do this:

return bc.FirstBlock == cell.Blocks.FirstBlock;

---

John Fenton