抛物线\(C\)：\(y ^{2} =8x\)的焦点为\(F\)，\(N\)为准线上一点，\(M\)为\(y\)轴上一点，且\( \overrightarrow {NM}\cdot \overrightarrow {NF} =0\)，若线段\(MF\)的中点\(E\)在抛物线\(C\)上，则\(\triangle MNF\)的面积为\((\:\:\:\:)\)
A. \(6 \sqrt {3}\)
B. \(6 \sqrt {2}\) C. \(3 \sqrt {2}\) D. \( \dfrac {3 \sqrt {2}}{2}\)
