ASP.NET MVC Model Binder Fails with Strings that look like version numbers? - asp.net-mvc

Question

This should be straight-forward, but here goes - we're using MVC4 to handle a multi-part Form request to upload a binary along with some meta-data via a strongly-typed view in MVC4.
One of the fields is a version number for the file (i.e. something like 0.0.6, 0.4.5-pre, etc...)
I'm getting the following error from the model binder when it tries to bind this version number field to the model field (string type):
{"The parameter conversion from type 'System.String' to type
'Models.NewFileVersion' failed because no type converter can convert
between these types."}
Specifically the error can be traced to our "VersionNumber" field - any ideas as to why this might be happening?
Edit: Source code below
NewFileVersion.cs
public class NewFileVersion
{
[Display(Name = "Version # (0.67, 0.66-pre, etc...)")]
[Required]
public string Version { get; set; }
[Required]
[StringLength(2000, ErrorMessage = "ChangeLog must be between 30 an 2000 characters", MinimumLength = 30)]
[Display(Name = "Version Notes (will be visible to end-users)")]
[DataType(DataType.MultilineText)]
public string ChangeLog { get; set; }
[Display(Name = "Target Platform")]
[UIHint("Enum")]
public FileType PlatformTarget { get; set; }
}
New.cshtml
#model ViewModels.NewFileVersion
#{
ViewBag.Title = "New";
}
<div class="container" id="main-content">
<div class="row">
<h2>
New</h2>
#using (Html.BeginForm("Create", "Files", FormMethod.Post, new { enctype = "multipart/form-data" }))
{
#Html.ValidationSummary(true)
<fieldset>
<legend>NewFileVersion</legend>
<div class="editor-label">
#Html.LabelFor(model => model.Version)
</div>
<div class="editor-field">
#Html.EditorFor(model => model.Version)
#Html.ValidationMessageFor(model => model.Version)
</div>
<div class="editor-label">
#Html.LabelFor(model => model.ChangeLog)
</div>
<div class="editor-field">
#Html.EditorFor(model => model.ChangeLog)
#Html.ValidationMessageFor(model => model.ChangeLog)
</div>
<div class="editor-label">
#Html.LabelFor(model => model.PlatformTarget)
</div>
<div class="editor-field">
#Html.EditorFor(model => model.PlatformTarget)
</div>
<div class="editor-label">
<label for="">
File:</label></div>
<div class="editor-field">
<input type="file" name="fileData" required="required" /></div>
<p>
<input type="submit" value="Upload File" />
</p>
</fieldset>
}
<div>
#Html.ActionLink("Back to List", "Index")
</div>
</div>
</div>
FilesController.cs
[HttpPost]
public ActionResult Create(NewFileVersion version, HttpPostedFileBase fileData)
{
//if our model is valid
if(ModelState.IsValid)
{
//etc....
}
ModelState.AddModelError("", "Invalid file submission");
return View("New", version);
}

Answer 1

Try renaming the version parameter for your Create action, e.g:
public ActionResult Create(NewFileVersion fileVersion, HttpPostedFileBase fileData) { ... }
The model binder may be getting confused between the string version model property and the NewFileVersion version action parameter.
You can see why this happens in the BindModel method, because the model has a property exactly matching the name of the action parameter it tries to bind as a simple type/model rather than a complex one.