C# 使用身份主键将新实体插入上下文
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Insert new entity to context with identity primary key
提问by P.Brian.Mackey
I want to insert a new record into my SQL table. I tried:
我想在我的 SQL 表中插入一条新记录。我试过：
public void CreateComment(int questionId, string comment)
{
QuestionComment questionComment = context.TableName.Create();//1*
questionComment.propertyThatIsNotAConstraint= questionId;
questionComment.body = comment;
context.QuestionComments.Add(questionComment);
context.SaveChanges();//ERROR...
}
1* I'm surprised to see intellisense tell me: "Note that the new entity is not added or attached to the set"
1* 我很惊讶地看到智能感知告诉我： “请注意，新实体没有添加或附加到集合中”
Error Reads:
错误读取：
"Violation of PRIMARY KEY constraint 'PK_TableName'. Cannot insert duplicate key in object 'dbo.TableName'. The duplicate key value is (0).\r\nThe statement has been terminated."
"违反 PRIMARY KEY 约束 'PK_TableName'。无法在对象 'dbo.TableName' 中插入重复键。重复键值为 (0)。\r\n语句已终止。"
The problem is that questionCommenthas its PK: questionComment.Iddefaulted to 0. It needs to be the next available Identity or otherwise not populated and do a "normal" identity insert.
问题是questionComment它的 PK:questionComment.Id默认为0. 它需要是下一个可用的身份或以其他方式未填充并执行“正常”身份插入。
How does entity framework expect me to handle this scenerio?
实体框架希望我如何处理这个场景？
As Requested:
按照要求：
//------------------------------------------------------------------------------
// <auto-generated>
// This code was generated from a template.
//
// Manual changes to this file may cause unexpected behavior in your application.
// Manual changes to this file will be overwritten if the code is regenerated.
// </auto-generated>
//------------------------------------------------------------------------------
namespace Feedback.Models
{
using System;
using System.Collections.Generic;
public partial class QuestionComment
{
public int id { get; set; }
public int questionId { get; set; }
public string body { get; set; }
public int commentIndex { get; set; }
}
}
采纳答案by P.Brian.Mackey
I fixed it by:
我通过以下方式修复它：
Go to SQL and make sure to the Table has the "Identity Specification" > Is Identity > set to Yes. Then update the *.edmx file if you had to make a DB change.
Check the *.edmx > Entity properties > StoreGeneratedPattern for the identity to ensure that it is set to Identity
转到 SQL 并确保表具有“身份规范”> 是身份 > 设置为是。如果必须更改数据库，则更新 *.edmx 文件。
检查 *.edmx > Entity properties > StoreGeneratedPattern 以获取标识以确保将其设置为Identity
回答by Steven Wexler
EF documentation states that the database generates a value when a row is inserted for columns configured with propConfig.HasDatabaseGeneratedOption(DatabaseGeneratedOption.Identity)
EF 文档指出，当为配置为的列插入一行时，数据库会生成一个值 propConfig.HasDatabaseGeneratedOption(DatabaseGeneratedOption.Identity)
http://msdn.microsoft.com/en-us/library/hh829109(v=vs.103).aspx
http://msdn.microsoft.com/en-us/library/hh829109(v=vs.103).aspx
In other words. EF won't care what value newCommentObject.Idis when inserting into the database. Instead, it'll allow the database to generate the next identity value.
换句话说。EF 不会关心newCommentObject.Id插入数据库时的值是什么。相反，它将允许数据库生成下一个标识值。
