MatDialog Error: No provider for InjectionToken mat-dialog-scroll-strategy

You need to include MatDialog Module in the imports.

import {MatDialogModule} from '@angular/material';
@NgModule({
   imports :[MatDialogModule],
   ...
})

Edit 2022

You need to include MatDialog Module in the imports.

import {MatDialogModule} from '@angular/material/dialog';
@NgModule({
   imports :[MatDialogModule],
   ...
})