角度表索引未使用multiTemplateDataRows指令定义

<mat-table [dataSource]="dataSource" multiTemplateDataRows>

    <!--Column definitions-->        
    <ng-container matColumnDef="{{columnProp.name}}" *ngFor="let columnProp of columnProps; let i = index;">
        <mat-header-cell *matHeaderCellDef mat-sort-header>
            {{columnProp.name}} {{i}}
        </mat-header-cell>

        <mat-cell *matCellDef="let element; let j = index;">
            <div>{{element[columnProp.name}} {{j}}</div>
        </mat-cell>
    </ng-container>

    <!--Row definitions-->
    <mat-header-row *matHeaderRowDef="displayedColumns"></mat-header-row>

    <!-- Row content-->
    <mat-row
        *matRowDef="let row; columns: displayedColumns; let k = index;"
        matRipple
        (click)="this.expandRow(row, k)">
    </mat-row>

    <!--Expanded row content-->
    <mat-row
        *matRowDef="let row; columns: ['expandedContent'];"
        [@detailExpand]="row == expandedElement ? 'expanded' : 'collapsed'">
    </mat-row>
</mat-table>

i 和 j 按预期显示,但当我单击我的行时,索引 k 显示为未定义。我做错了什么?