How to create and pass an object to OnPost?

Question

ASP.NET

Hello. I need to create a SentimentData object and pass it to OnPost.

<form method="post">
    <div>
        <label>Add Text</label>
        <input asp-for=SentimentData.SentimentText class="form-control" />
        <button type="submit" class="btn btn-primary">Save</button>
    </div>
</form>

public void OnPost(SentimentData SentimentData)
        {
            Text = SentimentData.SentimentText;
            Analysis.Evaluate(mlContext, Model, SplitDataView.TestSet);
            Analysis.UseModelWithSingleItem(mlContext, SentimentData, Model, Text);
        }

But i get null object