title: Blazor The name 'Invoke' doesn exist in the current context
body: <p>I am using Visual Studio 2019 Preview 4, .NET Core 3 RC1, </p>
  
  <p>I create a Blazor web-app (server blazor), I follow <a href="https://docs.devexpress.com/Blazor/DevExpress.Blazor.Base.DxTextBoxBase.TextChanged#remarks" rel="nofollow noreferrer">https://docs.devexpress.com/Blazor/DevExpress.Blazor.Base.DxTextBoxBase.TextChanged#remarks</a></p>
  
  <pre><code>&lt;DxTextBox Text="" TextChanged=@((newValue) =&gt; OnTextChanged(newValue))&gt;&lt;/DxTextBox&gt;
  &lt;button type="button" class="btn btn-primary" disabled=@IsDisabled&gt;Update Text&lt;/button&gt;
  
  @code {
      bool IsDisabled = true;
  
      void OnTextChanged(string newValue)
      {
          if (newValue != null)
              IsDisabled = false;
  
          Invoke(StateHasChanged);
      }
  }
  </code></pre>
  
  <p>I catch error </p>
  
  <blockquote>
    <p>The name 'Invoke' doesn exist in the current context</p>
  </blockquote>
  
  <p><a href="https://i.stack.imgur.com/ZyNkV.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/ZyNkV.png" alt="enter image description here"></a></p>
  
  <p>How to fix it?</p>