Question

My Model fields accepting numbers and empty string :

[DisplayName("Height")]
[RegularExpression (@"^\d*$", ErrorMessage="Height must be a number or left out   blank")]
public string Height { get; set; }

[DisplayName("Width")]
[RegularExpression(@"^\d*$", ErrorMessage = "Height must be a number or left out blank")]
public string Width { get; set; }

My view:

<%= Html.LabelFor(x => x.Width) %>:
<%= Html.TextBoxFor(x => x.Width) %>

<%= Html.LabelFor(x => x.Height) %>:
<%= Html.TextBoxFor(x => x.Height) %>

In controller action :

[HttpPost]

public ActionResult Edit(MyModeltype model)
{
    model.Width = String.IsNullOrEmpty(model.Width) ? "" : model.Width; //NEEDED?
    model.Height = String.IsNullOrEmpty(model.Height) ? "" : model.Height; //NEEDED?

    if (ModelState.IsValid)
        SaveSettings(model);

    return View("SomeView");
}

When I provide empty textboxes, Model.Width and .Height are passed as nulls and ModelState.IsValid is false. I just need to be able to pass the empty string. When omitting the regex attribute, same problem, so its not the regex. Thank you!

Answer 1

Try adding the DisplayFormat attribute to your model’s properties:

[DisplayFormat(ConvertEmptyStringToNull = false)]
[DisplayName("Height")]
[RegularExpression (@"^\d*$", ErrorMessage="Height must be a number or left out   blank")]
public string Height { get; set; }

[DisplayFormat(ConvertEmptyStringToNull = false)]
[DisplayName("Width")]
[RegularExpression(@"^\d*$", ErrorMessage = "Height must be a number or left out blank")]
public string Width { get; set; }

This will ensure empty textbox values are not converted to NULL.

Alternatively, you could explicitly define your getters and setters to convert nulls to empty strings:

private string _width;
public string Width
{
    get { return _width ?? string.Empty; }
    set { _width = value ?? string.Empty; }
}