It dissolves in $NH_4OH$ solution due to the formation of complex salt.
$AgCl + 2N{H_4}OH \to \mathop {[Ag{{(N{H_3})}_2}]Cl + 2{H_2}O}\limits_{{\text{Diamminesilver (I) chloride}}} $
$\left( {{C_2}O_4^{2 - } = } \right.$ ઓક્ઝલેટો $)$