title: Transfer list from .ts to .tsx
body: <p>I have a list that i get from SharePoint, and i want to use it as an items in my DropDownList in the .tsx file, i did it, but i have problem, i don't see items when i executed. But when i click on the dropDown, the items appear.
  When i debug the list which i get are realy empty in the first, it only fills up when i click on the DropDownList, i don't understand why my list are empty, i have same probleme whith all lists in my code. </p>
  
  <p>.ts </p>
  
  <pre><code>export default class DropWebPart extends BaseClientSideWebPart&lt;IDropPartProps&gt; {
    constructor() {
      super();
    }
    public render(): void {
      const element: React.ReactElement&lt;IFaqProps&gt; = React.createElement(drop, {
        dropList: this.getDropList()
      });
      ReactDom.render(element, this.domElement);
    }
    public getDropList(): IDropdownOption[] {
      let dropList: IDropdownOption[] = new Array();
      this._getData().then(response =&gt; {
        response.forEach((itemc: IOptionCategorie) =&gt; {
          dropList.push({ key: itemc.Categorie, text: itemc.Key });
        });
      });
      return dropList;
    }
    public _getData(): Promise&lt;IOptionCategorie[]&gt; {
      return sp.web.lists
        .getByTitle("Option")
        .items.select("Key", "Option")
        .get()
        .then((response: IOption[]) =&gt; {
          return response;
        });
    }
  }
  </code></pre>
  
  <p>.tsx</p>
  
  <pre><code>export default class drop extends React.Component&lt;IDropProps&gt; {
    public dropOption: IDropdownOption[];
    constructor(props: IDropProps) {
      super(props);
      this.dropOption = props.dropList;
      this.state = {
        selectedItem: undefined
      };
    }
    public render(): JSX.Element {
      const { selectedItem } = this.state;
      return (
        &lt;div&gt;
          &lt;FocusZone direction={FocusZoneDirection.vertical}&gt;
            &lt;Dropdown
              className={classNames.dropDown}
              label=""
              selectedKey={selectedItem ? selectedItem.key : ""}
              onChange={this._onChange}
              options={this.dropOption}
            /&gt;
            //liste
          &lt;/FocusZone&gt;
        &lt;/div&gt;
      );
    }
    private _onChange = (
      event: React.FormEvent&lt;HTMLDivElement&gt;,
      item: IDropdownOption
    ): void =&gt; {
      const { optionList } = this.props;
      this.setState({
        selectedItem: item
      });
    };
  }
  </code></pre>