How to convert Hex to Dec and vice-versa in c#

Question

I have a Hex values as below , And i wan't to convert this hex to decimal value with Signed Value.

i use System.Convert.ToUInt32() method to convert the hex string value to decimal string Value.

C# Code:

        String hs = "FFFFFFDF";    //Hex value which i got 
        uint decval = System.Convert.ToUInt32(hs, 16);
        string character = decval.ToString(); 

when i try to convert this i got unsigned Decimal value.so give some tips to make my code print the proper decimal value with signed value.