I've tried to adding a readonly attribute but this does not work.
@Html.TextBoxFor(m => m.Test.ClientNumber, new { readonly = "readonly", @name = "client" @id="validate" @class = "form-control" })
I was able to add the required attribute but the readonly won't work.
@Html.TextBoxFor(m => m.Test.ClientNumber, new { @readonly = "readonly", @name = "client", @id = "validate", @class = "form-control" })
I think you have missed @
for readonly
attribute.