SSRS comparing dates in an expression - sql

Question

I have some basic expressions to highlight certain fields:
=IIF(Fields!Failure.Value > 0, "Red", "Transparent")
However, I have another field that contains dates in the following format:
22/08/2016 22/08/2016 - each field can contain multiple dates.
This is stored in SQL as a VARCHAR.
I need to run a similar expression in my report to achieve the following:
If the date is 1 day older than the date the report is run, highlight the field. If the date is greater than 1 day older, highlight the field a different colour.
I#m familiar with basic expressions, but I can't think of an easy way to obtain the current date, and then compare between the two.

Answer 1

As others have said, you really shouldn't be using hacks like this...
But, this should work for you:
=iif(Len(Replace(Replace(Fields!DateField.Value," ",""), Format(Today, "dd/MM/yyyy"),"")) = 0, "Transparent" ,iif(Len(Replace(Replace(Replace(Fields!DateField.Value," ",""), Format(Today, "dd/MM/yyyy"),""), Format(Today().AddDays(-1), "dd/MM/yyyy"),"")) = 0, "Green", "Red"))
Essentially, remove the joining character (in this case, space) and then replace all instances of the current date in the given format. If there are any characters left, you have a date that doesn't match today. Then take that value and repeat for any instances of yesterday.
Obviously this will fall down if your date formatting changes.
But then you already knew that comparing dates as strings was a bad idea, right...

Answer 2

You can use the Split function to generate an array of values. Of course, you'll still need to select one of those to test. The following may get you going again.
=Iif(
CDate(
Split(
"21/08/2016, 22/08/2016",
","
).GetValue(0)
) < Today,
"True",
"False"
)
If, however, you are dealing with a date string that can contain any number of dates and you to test all of them then a simple SSRS expression won't handle that. Fortunately we can use a bit of custom code.
Right-click the report background and select report properties. Click the 'Code' item and paste the following into code box
Public Function TestDate(DateString As String) As String
Dim DatesArray() As String = Split(DateString)
Dim ReturnValue As String = "Transparent"
For Each d As String In DatesArray
If Date.Parse(d) = DateAdd(DateInterval.Day, -1, Date.Today) Then
ReturnValue = "Red"
End If
If Date.Parse(d) < DateAdd(DateInterval.Day, -1, Date.Today) Then
ReturnValue = "DarkRed"
End If
Next
Return ReturnValue
End Function
Now change the expression as below
=Code.TestDate("21/08/2016 22/08/2016")
I've used Date.Today in the VB to restrict the comparison of the date to the day. If you wanted to be more precise ie: the exact time, use Date.Now instead