ASP.NET MVC Checkbox Group
- by Greg Ogle
I am trying to formulate a work-around for the lack of a "checkbox group" in ASP.NET MVC. The typical way to implement this is to have check boxes of the same name, each with the value it represents.
<input type="checkbox" name="n" value=1 />
<input type="checkbox" name="n" value=2 />
<input type="checkbox" name="n" value=3 />
When submitted, it will comma delimit all values to the request item "n".. so Request["n"] == "1,2,3" if all three are checked when submitted. In ASP.NET MVC, you can have a parameter of n as an array to accept this post.
public ActionResult ActionName( int[] n ) { ... }
All of the above works fine. The problem I have is that when validation fails, the check boxes are not restored to their checked state. Any suggestions.
Problem Code: (I started with the default asp.net mvc project)
Controller
public class HomeController : Controller
{
public ActionResult Index()
{ var t = getTestModel("First");
return View(t);
}
[AcceptVerbs(HttpVerbs.Post)]
public ActionResult Index(TestModelView t)
{ if(String.IsNullOrEmpty( t.TextBoxValue))
ModelState.AddModelError("TextBoxValue", "TextBoxValue required.");
var newView = getTestModel("Next");
return View(newView);
}
private TestModelView getTestModel(string prefix)
{ var t = new TestModelView();
t.Checkboxes = new List<CheckboxInfo>()
{ new CheckboxInfo(){Text = prefix + "1", Value="1", IsChecked=false},
new CheckboxInfo(){Text = prefix + "2", Value="2", IsChecked=false}
};
return t;
}
}
public class TestModelView
{ public string TextBoxValue { get; set; }
public List<CheckboxInfo> Checkboxes { get; set; }
}
public class CheckboxInfo
{ public string Text { get; set; }
public string Value { get; set; }
public bool IsChecked { get; set; }
}
}
ASPX
<%
using( Html.BeginForm() ){
%> <p><%= Html.ValidationSummary() %></p>
<p><%= Html.TextBox("TextBoxValue")%></p>
<p><%
int i = 0;
foreach (var cb in Model.Checkboxes)
{ %>
<input type="checkbox" name="Checkboxes[<%=i%>]"
value="<%= Html.Encode(cb.Value) %>" <%=cb.IsChecked ? "checked=\"checked\"" : String.Empty %>
/><%= Html.Encode(cb.Text)%><br />
<% i++;
} %></p>
<p><input type="submit" value="submit" /></p>
<%
}
%>
Working Code
Controller
[AcceptVerbs(HttpVerbs.Post)]
public ActionResult Index(TestModelView t)
{
if(String.IsNullOrEmpty( t.TextBoxValue))
{ ModelState.AddModelError("TextBoxValue", "TextBoxValue required.");
return View(t);
}
var newView = getTestModel("Next");
return View(newView);
}
ASPX
int i = 0;
foreach (var cb in Model.Checkboxes)
{ %>
<input type="checkbox" name="Checkboxes[<%=i%>].IsChecked" <%=cb.IsChecked ? "checked=\"checked\"" : String.Empty %> value="true" />
<input type="hidden" name="Checkboxes[<%=i%>].IsChecked" value="false" />
<input type="hidden" name="Checkboxes[<%=i%>].Value" value="<%= cb.Value %>" />
<input type="hidden" name="Checkboxes[<%=i%>].Text" value="<%= cb.Text %>" />
<%= Html.Encode(cb.Text)%><br />
<% i++;
} %></p>
<p><input type="submit" value="submit" /></p>
Of course something similar could be done with Html Helpers, but this works.
