Using collations
eg:
if ('a'='A' Collate Latin1_General_CI_AI)
print'same 1'
else
print 'different 1'
if ('a'='A' Collate Latin1_General_CS_AI)
print'same 2'
else
print 'different 2'
The CS in the collation name indicates Case Sensitive (and CI, Case Insensitive). The AI/AS relates to accent sensitivity.
And If you want to check in C# code then you can Use
IsUpper()
Or
IsLower()
Methods.