How can I position a dialog above the triggering button?

You can adjust position of dialog component using updatePosition() method of MdDialogRef. first import this line in your dialog component

import { MdDialog, MdDialogConfig, MdDialogRef } from '@angular/material';

in constructor use this

constructor(public dialModalRef: MdDialogRef<any>) { }

then from inside dialog modal component call this method anywhere you want

 changePosition() {
        this.dialModalRef.updatePosition({ top: '50px', left: '50px' });
    }

read more about it here https://material.angular.io/components/component/dialog

i hope this will help :)

A better way to do this is to inject the button element and pass it into the dialog. This way, the dialog has the full context on how to size it up/position it (and leverage the element.getBoundingClientRect() function):

Dialog Component:

import { Component, ElementRef, Inject, OnInit } from '@angular/core';
import { MAT_DIALOG_DATA, MatDialogConfig, MatDialogRef } from '@angular/material';

@Component({
  selector: 'app-dialog-component',
  templateUrl: './dialog.component.html',
  styleUrls: ['./dialog.component.scss']
})
export class MyDialogComponent implements OnInit {
  private readonly _matDialogRef: MatDialogRef<MyDialogComponent>;
  private readonly triggerElementRef: ElementRef;
  constructor(_matDialogRef: MatDialogRef<MyDialogComponent>,
              @Inject(MAT_DIALOG_DATA) data: { trigger: ElementRef }) {
    this._matDialogRef = _matDialogRef;
    this.triggerElementRef = data.trigger;
  }

  ngOnInit() {
    const matDialogConfig: MatDialogConfig = new MatDialogConfig();
    const rect = this.triggerElementRef.nativeElement.getBoundingClientRect();
    matDialogConfig.position = { left: `${rect.left}px`, top: `${rect.bottom - 50}px` };
    matDialogConfig.width = '300px';
    matDialogConfig.height = '400px';
    this._matDialogRef.updateSize(matDialogConfig.width, matDialogConfig.height);
    this._matDialogRef.updatePosition(matDialogConfig.position);
  }
  cancel(): void {
    this._matDialogRef.close(null);
  }
}

Usage:

onShowDialog(evt: MouseEvent): void {
  const target = new ElementRef(evt.currentTarget);
  const dialogRef = this._matDialog.open(MyDialogComponent, {
    data: { trigger: target }
  });
  dialogRef.afterClosed().subscribe( _res => {
    console.log(_res);
  });
}

The styles from your component won't affect its parents. Since the dialog-container is the parent of your ThankYouComponent, it won't override its position.

As a workaround, you can add the positioning to your global styles.css.

⚠️ Caution though, this affects all of your dialogs! ⚠️

styles.css

mat-dialog-container {
  position: fixed;
  left: 20%;
  top: 0%
  background-color: white;
  z-index: 100000;
}

const dialogRef = this.dialog.open(DialogOverviewExampleDialog, {
      width: '250px',
      data: { name: this.name, animal: this.animal },
      position: {
        top: '0px',
        left: '0px'
      }
    });