Public ReadOnly..

Hello Frinds..
if any calss varibale as ReadOnly
like
Public readonly bool alpha=false;


what is this means exactly.. can we assing any value to alpha at run time in C#Code..
bec this colum value I need to take from database..
when I am asing clumn value to tthis table i am getting error like..
A readOnly field Cannot be assigned to(Except in a contruxtor or variable intializer)


can any one help me out..


thanks

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