Chris Hays's Reporting Services Sleazy Hacks Weblog : Sleazy Hacks

"Continued" Header on Subsequent Pages

ChrisHays — Thu, 28 Sep 2006 01:40:00 GMT

Question:
How can I repeat a group header on each page, but have it say "MyGroup (continued)" on all but the first page?

Answer:
Since pagination is determined long after the report has been fully processed, there's no way for the body of the report to reference any page information. As a result, we're going to have to resort to a trick wherein something in the page header can be made to look as if it is the group header.

The following assumes you are using a table and have no table header but can be readily adapted to other situations.

Step 1: Turn off RepeatOnNewPage on your group header

Step 2: Duplicate the group header information in a hidden column
You're going to need the group header text to always be present on the page, even when the group header itself isn't present. The easiest way is to add a hidden column to the table and then copy the group header textbox into the detail row in that column. Make careful note of the names of both the group header textbox (which I'll call GroupHeader) and the copy (which I'll call GroupCopy)

Step 3: Copy the first GroupHeader and first GroupCopy to the page header
In the page header, add two textboxes with the following expressions:
=First(ReportItems!GroupHeader.Value)
=First(ReportItems!GroupCopy.Value)
Make careful note of the names of both these textboxes (which I'll call FirstGroupHeader and FirstGroupCopy). Run the report and notice the behavior: FirstGroupHeader is the same as FirstGroupCopy only if it appears at the top of the page. Mark both textboxes as Hidden=True

Step 4: Copy the GroupCopy textbox into the page header and add "continued"
In the page header, add a textbox with the following expression:
=First(ReportItems!GroupCopy.Value) + " (continued)"
Align and size the textbox to match the GroupHeader textbox exactly. Now when you run the report, you'll see both the normal group header and the Continued group header

Step 5: Conditionally hide the Continued header textbox
Ideally, the next step would be to set the Hidden expression on the Continued header textbox to this:
=ReportItems!FirstGroupHeader.Value=ReportItems!FirstGroupCopy.Value
Unfortunately, this won't work due to a slightly overzealous publishing restriction against using multiple report item references within a single expression in a page header item [which was intended to prevent potentially bad things like Sum(textbox1/textbox2)].
However, we can bypass this publishing restriction by passing in the report items collection to a custom function.
Add the following to the report's Code block:
public function HideHeader(Items as ReportItems) as Boolean
return Items("FirstGroupHeader").Value = Items("FirstGroupCopy").Value
end function
Now set the Hidden property of the Continued header to:
=Code.HideHeader(ReportItems)

Note: In the event you will always page break at the end of a group, there is a much simpler approach. You can skip steps 3 and 5 and instead set the Hidden property of the Continued header to:
=Not(ReportItems!GroupHeader.Value Is Nothing)

A full working sample of continued headers on subsequent pages is attached.

Reset Page Number On Group

ChrisHays — Fri, 06 Jan 2006 05:14:00 GMT

Question:
How can I reset my page number back to 1 every time I get a group break?

Answer:
Resetting the page number on group breaks isn't natively supported, but it can be achieved by tracking group breaks in a shared variable and subtracting off the page offset of the first page of the group from the current page number.

Step 1: Make sure there's a textbox in the report which contains the group expression

Step 2: Add shared variables to track the current group and page offset
Shared offset as Integer
Shared currentgroup as Object

Step 3: Add a custom function to set the shared variables and retrieve the group page number
Public Function GetGroupPageNumber(group as Object, pagenumber as Integer) as Object
  If Not (group = currentgroup)
   offset = pagenumber - 1
   currentgroup = group
  End If
  Return pagenumber - offset
End Function

Step 4: Use the function in the page header or footer
=Code.GetGroupPageNumber(ReportItems!Category.Value,Globals!PageNumber)

Note: Because this uses static variables, if two people run the report at the exact same moment, there's a slim chance one will smash the other's variable state (In SQL 2000, this could occasionally happen due to two users paginating through the same report at the same time, not just due to exactly simultaneous executions) If you need to be 100% certain to avoid this, you can make each of the shared variables a hash table based on user ID (Globals!UserID).

A full working sample of page number reset on group is attached.

Centered Images

ChrisHays — Wed, 27 Oct 2004 22:38:00 GMT

Question:
I have variable sized images I want to display in a table column. How can I center these images without stretching them to fill the table cell?

Answer:
While there is no automatic centering behavior for the Image control, you can simulate this by writing an expression for PaddingLeft and PaddingTop to result in a centered image.

Step 1: Clip, don't Fit

Set the Sizing property of the Image control to Clip. In a table cell, this is the only setting that won't resize your image. (If your image gets automatically resized, the calculations below won't work.)

Step 2: Give yourself room to grow

Make your column and row large enough to accomodate your largest image so that the image won't clip.

Step 3: Turn off CanGrow

For all other cells in the row, turn off CanGrow, so ensure long textual contents won't cause the row to increase in size (thereby invalidating the calculations below).

Step 4: Reference System.Drawing

To determine the size of the image, you'll need to add a reference to the System.Drawing assembly in your report. This is in the Report Properties dialog on the References Tab.

Step 5: Calculate padding

To determine the size of the image, you'll need to load the image from your field into a memory stream and from there load it into a .Net Image object. Since fields are of type Object, you'll need to cast it to a byte array before loading it into a memory stream.

ImageWidthInPixels = System.Drawing.Image.FromStream(new System.IO.MemoryStream(CType(Fields!Photo.Value,Byte()))).Width

From there, you can calculate the half of the difference between the width of the image and the width of the column.

Padding = (ColumnWidthInInches-ImageWidthInPixels/DPI)/2

DPI is typically 96

The padding property takes a size, which is a string including the size and the units.

PaddingLeft = CStr(Round(Padding,2)) & "in"

Here's the expression fully expanded:

=CStr(Round((3-System.Drawing.Image.FromStream(new System.IO.MemoryStream(CType(Fields!Photo.Value,Byte()))).Height/96)/2,2))&"in"

Now just do the same thing for PaddingTop and you've got a fully centered image.

A full working sample of centered images is attached.

Green-Bar Matrix

ChrisHays — Tue, 31 Aug 2004 04:22:00 GMT

Question:
How can I get a green-bar effect (alternating colors) in a matrix?

Answer:
For a green-bar table, you can simply use a background color expression like this: =iif(RowNumber(Nothing) Mod 2,"Green","White")
However, there is currently no GroupNumber() function on which to base a green-bar calculation in a matrix.
GroupNumber can be (mostly) simulated by using the RunningValue function to get a running distinct count of group expression values.
However, the trickiest part of green-bar in a matrix is the fact that some matrix cells may contain no data at all. This makes the group number calculation incorrect for empty cells.
To work around this, you need to effectively calculate the group number in the row header and then use that value inside the data cells.

Step 1: Add a (fake) inner row grouping
Select the innermost row grouping in your matrix. Right-click and select Insert Group.
For the group expression, group on a constant, such as =1

Step 2: Calculate the name of the color in the inner row grouping header
In the Value property of the newly created grouping header, add a calculation for the desired color based on a running value of a count distinct of the containing group expression.
For example: =iif(RunningValue(Fields!Country.Value,CountDistinct,Nothing) Mod 2, "AliceBlue", "White")
Note: If you have more than one row grouping, you may need to do the count distinct on the combination of all group expressions, like this:
=iif(RunningValue(Fields!Country.Value & CStr(Fields!Year.Value),CountDistinct,Nothing) Mod 2, "AliceBlue", "White")

Step 3: Set the background color of the inner row grouping header to =Value

Step 4: Set the background color of the matrix data cell to the value of the inner row grouping header
For example: =ReportItems!ColorNameTextbox.Value

Step 5: Set the background color of the outer row grouping header
You'll need to use the same expression here that you used for the Value of the inner row grouping header.

Step 6: "Cloak" the inner row grouping header (so it looks like part of of the outer grouping header)
Set the right border style of the outer grouping header to None.
Set the left border style of the inner grouping header to None.
Set the font weight of the inner grouping header to 1 pt.
Set the font color of the inner grouping header to =Value.
Set the CanGrow property of the inner grouping header to False.
Drag the inner grouping header to be as narrow as possible.
Optional: Hand-edit the RDL to set the width of the inner grouping header to 0in.

A full working sample of green-bar matrix is attached.