The Variable @abc has already been Declare Could not Update a list of Fields of Query in SSRS Report

A comman Mistake while working with SSRS Report that SSRS is Case Sensitive while SQL is not
The mistake what i was doing that i created an sql query for the Report where i declared lots of variable
what i did like
--take an Example
I was having two parameters in the Report StartDate and EndDate
 My parameter was @StartDate in the Report
In my query i was using like this @startDate --small s

Select empname,address from employee where
empdob between @startDate and @EndDate

In sql the  query was working file but when i run the same query using SSRS query designer i saw report was asking for one more Parameter i start date

I clicked ok after passing values to Paramter

The Reason behind this error the SSRS considered @startDate as New Parameter of Report I
changed @startDate to @StartDate the Report works without any issue.

Note-@startDate has Started from small s and @StartDate with Capital S so SSRS consider these as two paramter these is a comman mistake so always keep Paramters in same Case both in SQL query and SSRS Report.