“当IDENTITY_INSERT设置为OFF时，无法为表{Tags}中的标识列插入显式值。”

Question

I keep getting this error when trying to add new instances of my Tag class to the database. The error is specific to my Tags DB table, so I'm guessing my code is somehow trying to pass an ID value to the column which is already the identity and auto-incrementing.

Seen below is a copy of the relevant information from the CreatePost method in the PostController:

public ActionResult CreatePost(Post postFromForm, string tags)
    {
        postFromForm.CreatedOn = DateTime.Now;

        postFromForm.Tags = new List<Tag>();

        string[] tagList = tags.Split(' ');
        foreach (var tag in tagList)
        {
            Tag NewTag = new Tag();
            NewTag.Name = tag;
            postFromForm.Tags.Add(NewTag);
        }

        using (var dbContext = new blogEntities())
        {
            dbContext.Posts.Add(postFromForm);
            dbContext.SaveChanges();
        }

And a look at the form fields which pass parameters into the method:

 @Html.TextBox("title", "", new { @class = "form-control", @placeholder = "Title" })
 @Html.TextArea("body", "", new { @class = "BodyEdit form-control", @placeholder = "Start typing here..." })
 @Html.TextBox("tags", "", new { @class="form-control", @placeholder="Tags" })

 <input type="hidden" name="createdby" value="@Session["username"]" />    
 <input type="submit" class="btn btn-primary pull-right" value="Post" />

And for good measure, a look at my classes:

public partial class Tag
{
    public Tag()
    {
        this.Posts = new HashSet<Post>();
    }

    public int Id { get; set; }
    public string Name { get; set; }

    public virtual ICollection<Post> Posts { get; set; }
}


public partial class Post
{
    public Post()
    {
        this.Comments = new HashSet<Comment>();
        this.Tags = new HashSet<Tag>();
    }

    public string Title { get; set; }
    public string Body { get; set; }
    public System.DateTime CreatedOn { get; set; }
    public int Id { get; set; }
    public Nullable<System.DateTime> EditedOn { get; set; }
    public string CreatedBy { get; set; }

    public virtual ICollection<Comment> Comments { get; set; }
    public virtual ICollection<Tag> Tags { get; set; }
}

Any insights would be much appreciated - I've been banging my head against the wall with this all afternoon. And if possible does anybody know if simply changing the value of IDENTITY_INSERT (which I tried, didn't work) is a solution for the cause rather than the symptoms?

Answer 1

Possible answer

Update your edmx file to reflect any changes you may have made in the database. If the database automatically assigns the value, you should see the "IsDbGenerated=true" attribute in your designer file under that property. If it's not there, you can add it manually.

Entity Framework error: Cannot insert explicit value for identity column in table