[英]Saving Many-To-Many Relationship with Entity Framework to MySQL
我有BOM和項目表,它們是多對多的。
以下是我的BOM代碼
public class BOM
{
public int Id { get; set; }
[Required(ErrorMessageResourceType = typeof(Resource), ErrorMessageResourceName = "ThisFieldIsRequired")]
[StringLength(OwnConstants.StringLengthShort)]
public string BOMRevision { get; set; }
[Required(ErrorMessageResourceType = typeof(Resource), ErrorMessageResourceName = "ThisFieldIsRequired")]
[Index("BOM Code", 1, IsUnique = true)]
[StringLength(OwnConstants.StringLengthShort)]
public string BOMCode { get; set; }
[Required(ErrorMessageResourceType = typeof(Resource), ErrorMessageResourceName = "ThisFieldIsRequired")]
[StringLength(OwnConstants.StringLengthShort)]
public string Title { get; set; }
public virtual ICollection<Project> Projects { get; set; }
public virtual ICollection<BOMDetail> BOMDetails { get; set; }
}
下面是我的Project代碼
public class Project
{
public int Id { get; set; }
[Required(ErrorMessageResourceType = typeof(Resource), ErrorMessageResourceName = "ThisFieldIsRequired")]
[Index("Project Code", 1, IsUnique = true)]
[StringLength(OwnConstants.StringLengthShort)]
public string ProjectCode { get; set; }
[Required(ErrorMessageResourceType = typeof(Resource), ErrorMessageResourceName = "ThisFieldIsRequired")]
[Index("Description", 1, IsUnique = true)]
[StringLength(OwnConstants.StringLengthShort)]
public string Description { get; set; }
[Required(ErrorMessageResourceType = typeof(Resource), ErrorMessageResourceName = "ThisFieldIsRequired")]
public int? CustomerId { get; set; }
public virtual Customer Customer { get; set; }
public virtual ICollection<BOM> BOMs { get; set; }
}
我正在嘗試將新條目保存到BOM 。 但是,當我嘗試添加Project時,我將變為null。 下面是我要保存的代碼。
public override void Save()
{
using (var db = new ApplicationDbContext())
{
var currentID = (Entity as BOM).Id;
var ExistingBOM = db.BOMs.SingleOrDefault(x => x.BOMCode == BOMCodeTextEdit.Text);
if (ExistingBOM != null)
{
XtraMessageBox.Show("Record Exist", "Error", MessageBoxButtons.OK);
return;
}
if (currentID == 0)
{
BOM boms = new BOM()
{
BOMRevision = BOMRevisionTextEdit.Text,
BOMCode = BOMCodeTextEdit.Text,
Title = TitleTextEdit.Text,
};
Project proj = new Project();
int Project_Id = Convert.ToInt32(ProjectsLookUpEdit.EditValue);
proj = db.Projects.SingleOrDefault(x => x.Id == Project_Id);
db.Projects.Attach(proj);
boms.Projects.Add(proj); // <== getting null here
}
db.SaveChanges();
XtraMessageBox.Show("Save Successfully", "Information", MessageBoxButtons.OK);
}
}
我錯過了什么嗎?
更新的代碼
int Project_Id = Convert.ToInt32(ProjectsLookUpEdit.EditValue);
var proj = db.Projects.Where(x => x.Id == Project_Id).ToList();
boms.Projects.Add(proj);
db.BOM.Add(boms);
您嘗試在需要添加ICollection<T>
位置添加單個記錄,更改查詢並將列表改為單個項目。
var projs =db.Projects.Where(x => x.Id == Project_Id).ToList();
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