How to Set regular expression for accept Arabic and English letters only in Devexpress TextBox ?

Hi all

i have devexpress tools , i have added an textbox and i want user to input letters only in this textbox (Arabic Or English ) and problrm is devexpress textbox don't work with ajax tools " filter TextBox "

i can set it to accept numbers only 

ValidationExpression="\b[0-9]*\.*[0-9]+\b"

so how i can set it to accept letters only ( Arabic or English ) ?