我已经设法通过更改代码中的ngModel"filter_defaultSelectedValue"来限制这种特殊情况. 如果在对话框中未选择任何内容，则将ngModel设置为某个先前设置的值:

I've managed to condition this special case by changing in code the ngModel "filter_defaultSelectedValue". If inside the dialog nothing was selected, ngModel is set to some previously set value:

this.filter_defaultSelectedValue = this.lastSelection;

如果选择了对话框中的某些内容，则让我通过mat-select将我的"filter_defaultSelectedValue"更改为该选定值.

If something inside dialog was selected, then I let mat-select change my "filter_defaultSelectedValue" to that selected value.