message: one more bug :)
diff: @@ -1194,6 +1194,7 @@ export class ColumnCollection<rowType extends Entity<any>> {
  async add(...columns: ColumnSetting<rowType>[]):Promise<void>;
  async add(...columns: string[]):Promise<void>;
  async add(...columns: any[]) {
  + var promises: Promise<void>[] = [];
  for (let c of columns) {
  let s: ColumnSetting<rowType>;
  let x = c as ColumnSetting<rowType>;
  @@ -1217,12 +1218,13 @@ export class ColumnCollection<rowType extends Entity<any>> {
  }
  else {
  - await this.buildDropDown(x);
  + promises.push(this.buildDropDown(x));
  }
  this.items.push(x);
  }
  + Promise.all(promises);
  return Promise.resolve();
  }
  async buildDropDown(s: ColumnSetting<any>) {
  