cshtml aspfor getter not working but the setter

I try to get the data of an input via asp-for from a cshtml page to a cshtml.cs page.

cshtml

<div class="form-group">
    <label class="col-sm-2 control-label">Name</label>
    <div class="col-sm-10">
        <textarea name="InputNameEvent" asp-for="NameEvent" class="form-control" placeholder="Name"></textarea>
    </div>
</div>

cshtml.cs

[Required]
[MinLength(5)]
[MaxLength(1024)]
public string NameEvent { get; set; }

public string Name2;

public void OnGet()
{
  NameEvent = "Test";
}
 public void OnPost()
 {
     Name2 = NameEvent;
 }

Test is shown in the Textarea, but in OnPost() NameEvent is NULL