使用 MdDialog 報錯，需要在AppModule 中依賴注入么？

TS代碼片斷：

import { MdDialog } from '@angular/material';

constructor(private dialog: MdDialog) { }

openNewProjectDialog() {
    this.dialog.open(NewProjectComponent);
}

報錯提示：

`core.js:1449 ERROR Error: Uncaught (in promise): Error: StaticInjectorError(AppModule)[ProjectListComponent -> MdDialog]:
StaticInjectorError(Platform: core)[ProjectListComponent -> MdDialog]:

NullInjectorError: No provider for MdDialog!

Error: StaticInjectorError(AppModule)[ProjectListComponent -> MdDialog]:
StaticInjectorError(Platform: core)[ProjectListComponent -> MdDialog]:

NullInjectorError: No provider for MdDialog!`