I'm getting this error on EF.
Cannot insert explicit value for identity column in table
'GroupMembers_New' when IDENTITY_INSERT is set to OFF.
GroupMember groupMember = new GroupMember();
groupMember.GroupId = group.Id;
groupMember.UserId = (new UserId(group.Owner));
//groupMember.Id = _groupContext.GroupMembers.Count();
I have run into this before. This error means you are trying to assign a value explicitly to a column where the database automatically assigns it.
Suggestion: 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.