code behind validation

 Hi All,
i want to do validation for below 2 cases.
Cases:
1.Alphabets
2.Numeric
in both the cases i have done the corresponding validation for a given input using Regex in code behind.
the issue iam facing here is like
Alphabet case
ex:' hi'
here the above (' hi),white/empty space added before to it.this space can be anywhere like it can be middle,last of the inputs.no  issue..it shouldn't be before any gn inputs.
it is applicable for both the cases(Alphabets and numeric).
i should alert them if input comes as above one i mentioned in the ex.
Note:
This validation only be done at code behind page(.aspx.cs) of asp.net 2.0 or above.no other validation such as server side(asp.net server controls) or client ...