I am using ASP.Net MVC 6
My Controller Function:
// POST: MyManyToManies/Create
[HttpPost]
[ValidateAntiForgeryToken]
public IActionResult Create(MyManyToMany myManyToMany)
{
if (ModelState.IsValid)
{
_context.TestManyToMany.Add(myManyToMany);
_context.SaveChanges();
//==========Get Last Inserted ID==============//
int LastInsertedID = _context.TestManyToMany.Max(c => c.ID);
string[] agencies = Request.Form["agencies"].ToArray();
MyManyRelAgency Rel = new MyManyRelAgency();
foreach (string aitem in agencies)
{
int d = int.Parse(aitem);
Rel.AgencyID = d;
Rel.MyManyID = LastInsertedID;
_context.Add(Rel);
_context.SaveChanges();
}
return RedirectToAction("Index");
}
return View(myManyToMany);
}
My Model 1
public class MyManyToMany
{
public int ID { get; set; }
public string FirstName { get; set; }
}
My Model 2 for inserting related items ids:
public class MyManyRelAgency
{
[Key]
public int ID { get; set; }
public int MyManyID { get; set; }
public int AgencyID { get; set; }
}
My View:
@model UNTest.Models.MyManyToMany
@{
ViewData["Title"] = "Create";
}
<h2>Create</h2>
<form asp-action="Create">
<div class="form-horizontal">
<h4>MyManyToMany</h4>
<hr />
<div asp-validation-summary="ValidationSummary.ModelOnly" class="text-danger"></div>
<div class="form-group">
<label asp-for="FirstName" class="col-md-2 control-label"></label>
<div class="col-md-10">
<input asp-for="FirstName" class="form-control" />
<span asp-validation-for="FirstName" class="text-danger" />
</div>
</div>
<div class="form-group">
<label class="col-md-2 control-label">Province</label>
<div class="col-md-10">
@Html.DropDownList("agencies", (List<SelectListItem>)ViewBag.options, htmlAttributes: new { @class = "form-control",@multiple="multiple" })
</div>
</div>
<div class="form-group">
<div class="col-md-offset-2 col-md-10">
<input type="submit" value="Create" class="btn btn-default" />
</div>
</div>
</div>
</form>
<div>
<a asp-action="Index">Back to List</a>
</div>
When I click on insert I get bellow error:
Cannot insert explicit value for identity column in table 'MyManyRelAgency' when IDENTITY_INSERT is set to OFF
If you need insert a value on ID, try this
[Required, Key, DatabaseGenerated(DatabaseGeneratedOption.None)]
public int ID{ get; set; }
You are getting this error with EF when you are adding an entity with Id. Usually this entity is already exists in DB. To modify an entity use example below:
_context.TestManyToMany.Add(myManyToMany);
change to
foreach(var e in myManyToMany)
_context.Entry(e).State = EntityState.Modified;
If this is something you want to do, when your id-column is an identity column, you need to run SET IDENTITY_INSERT dbo.YOUR_TABLE_NAME ON;
for it to work. This enables you to insert an ID into the identity column. However, you don't need to specify an ID when inserting a new row into a table with an identity column :)
Or are you trying to do an update of an already existing row?
After studying this site:
http://www.entityframeworktutorial.net/entityframework6/addrange-removerange.aspx
by using List and AddRange
I solved my problem, please see below code for Create Function it works perfect:
// POST: MyManyToManies/Create
[HttpPost]
[ValidateAntiForgeryToken]
public IActionResult Create(MyManyToMany myManyToMany)
{
if (ModelState.IsValid)
{
_context.TestManyToMany.Add(myManyToMany);
_context.SaveChanges();
//==========Get Last Inserted ID==============//
int LastInsertedID = _context.TestManyToMany.Max(c => c.ID);
string[] agencies = Request.Form["agencies"].ToArray();
//MyManyRelAgency Rel = new MyManyRelAgency();
IList<MyManyRelAgency> TheRel = new List<MyManyRelAgency>();
foreach (string aitem in agencies)
{
int d = int.Parse(aitem);
TheRel.Add(new MyManyRelAgency() { AgencyID = d, MyManyID = LastInsertedID });
//Rel.AgencyID = d;
//Rel.MyManyID = LastInsertedID;
}
_context.MyManyToManyRelWithAgency.AddRange(TheRel);
_context.SaveChanges();
return RedirectToAction("Index");
}
return View(myManyToMany);
}
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