Update object in database using Entity Framwork Mvc asp.net - trying with EntityState.Modified

<p>Hello,&nbsp;</p>
<p>I have a problem when I am trying to update Supplier in database.&nbsp;</p>
<p>My database consist of four tables: Supplier, Town, Street and Adress.&nbsp;</p>
<p>Columns of table Town: TownID(primary key), NameTown</p>
<p>Columns of table Street: TownID,StreetID (composite primary key),NameStreet</p>
<p>Columns of table Adress: TownID,StreetID,NumberAdress(<wbr>all of these columns are composite primary key)</p>
<p>Columns of table Supplier: SupplierID,NameSupplier,<wbr>TownID,StreetID,NumberAdress,NumberOfPhone, Email</p>
<p>This is my code in Controller:</p>
<p>private fpisEntities db = new fpisEntities();<br>
[HttpGet]<br>
public ActionResult Edit(int id)<br>
{<br>
<br>
Supplier supplier= db.Supplier.Find(id);<br>
<br>
return View(supplier);<br>
}<br>
[HttpPost]<br>
[ValidateAntiForgeryToken]<br>
public ActionResult Edit( Supplier supplier)<br>
{<br>
<br>
try<br>
{<br>
if (ModelState.IsValid)<br>
{<br>
<br>
db.Entry(supplier).State = EntityState.Modified;<br>
<br>
db.SaveChanges();<br>
return RedirectToAction(&quot;ChangeSupplier&quot;);<br>
}<br>
}<br>
catch (DataException /* dex */)<br>
{<br>
//Log the error (uncomment dex variable name after DataException and add a line here to write a log.)<br>
ModelState.AddModelError(&quot;&quot;, &quot;Unable to save changes. Try again, and if the problem persists, see your system administrator.&quot;);<br>
}<br>
<br>
return View(supplier);<br>
}</p>
<p>This is my View: for ChangeSupplier</p>
<p><br>
@model FpisNada.Models.Supplier<br>
@{<br>
ViewBag.Title = &quot;Index&quot;;</p>
<p>Layout = null;<br>
}</p>
<p>@using (Html.BeginForm())<br>
{<br>
@Html.AntiForgeryToken()<br>
@Html.ValidationSummary(true)</p>
<p>@Html.TextBoxFor(model =&gt; model.<span>SupplierID</span>, new { @placeholder = &quot;pib dobavljaca&quot;, style = &quot; float:left&quot; })</p>
<p>&lt;div class=&quot;col-md-9&quot;&gt;<br>
@if (ViewBag.ListaMesta != null)<br>
{<br>
@Html.DropDownListFor(m =&gt; m.<span>TownID</span>, ViewBag.ListaMesta as SelectList, &quot;--select mesto--&quot;, new { @class = &quot;form-control&quot;, style = &quot; float:left&quot; })</p>
<p>}</p>
<p>@Html.DropDownListFor(m =&gt; m.<span>StreetID</span>, new SelectList(&quot;&quot;), &quot;--select ulicu--&quot;, new { @class = &quot;form-control&quot;, style = &quot; float:left&quot; })</p>
<p><br>
&lt;div class=&quot;container&quot;&gt;</p>
<p><br>
@Html.TextBoxFor(model =&gt; model.<span>NumberAdress</span>, new { @class = &quot;form-control&quot;})<br>
@Html.TextBoxFor(model =&gt; model.Email, new { @class = &quot;form-control&quot; })<br>
@Html.TextBoxFor(model =&gt; model.<span>NameSupplier</span>, new { @class = &quot;form-control&quot; })<br>
@Html.TextBoxFor(model =&gt; model.NumberOfPhone, new { @class = &quot;form-control&quot; })<br>
&lt;/div&gt;<br>
&lt;/div&gt;<br>
&lt;input type=&quot;submit&quot; value=&quot;Edit&quot; /&gt;<br>
}</p>
<p><span>I appreciate any advise or help!&nbsp;</span></p>