IIf problem

I'm using that expression in a select statment in generic query designer, but there is a problem with it. I'm wondering what would that be.

IIf(Parameters!StartDate.Value = "" or Parameters!EndDate.Value = "", "", "where (Date between '" & Parameters!StartDate.Value & "' and '" & Parameters!EndDate.Value & "')")

A double-quote character within a string literal is escaped by a preceding double-quote. So, the second argument of IIf() should look like:

"where (Date between '"" & Parameters!StartDate.Value & ""' and '"" & Parameters!EndDate.Value & ""')"
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/vbls7/html/vblrfvbspec2_4_4.asp
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Visual Basic Language Specification

2.4.4 String Literals

A string literal is a sequence of zero or more Unicode characters beginning and ending with an ASCII double-quote character, a Unicode left double-quote character, or a Unicode right double-quote character. Within a string, a sequence of two double-quote characters is an escape sequence representing a double quote in the string.
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|||Thank you Deepak for your help. Actually it worked with one double quote, the problem was in the condition (Parameters!StartDate.Value = ""), I replaced it by IsNothing(Parameters!StartDate.Value) and it worked fine.