插入新记录之前检查记录是否存在 [英] Check the existence of a record before inserting a new record

问题描述

我使用的是Ado.net实体框架是第一次，我需要检查之前，我把它插入到数据库记录的存在。优选地，如果存在AuthodSSID，而不是关键（的AuthorID）我想搜索。我使用VS2010，框架4. System.Data.Entity的是3.5.0.0。

我用Google搜索，但没有发现答案这个问题。

  PublishingCompanyEntities publishContext; 
 publishContext =新PublishingCompanyEntities（）; 
 
私人无效createNew_Click（对象发件人，EventArgs五）
 {
作者newAuthor =新的作者（）; 
 newAuthor.FirstName = firstName.Text; 
 newAuthor.LastName = lastName.Text; 
 newAuthor.AuthodSSID = 20; 
 newAuthor.AuthorID = 10 
 //检查记录存在这里
 publishContext.AddToAuthor（newAuthor）; //插入如果它不存在
 
} 
  

解决方案

要检查是否有记录存在的唯一方法是查询记录并查看是否有回来：

  VAR existingAuthorCount = publishContext.Author.Count（A => a.AuthodSSID == 20 ）; 
如果（existingAuthorCount == 0）
 {
 //做你插入
} 
  

I'm using the Ado.net Entity Framework for the first time and I need to check if this record exist before I insert it to the database. Preferably I'd search if AuthodSSID exists and not the key (AuthorID). I'm using VS2010, Framework 4. System.Data.Entity is 3.5.0.0.

I googled, but found no answer for this question.

PublishingCompanyEntities publishContext;
publishContext = new PublishingCompanyEntities();

private void createNew_Click(object sender, EventArgs e)
{
    Author newAuthor = new Author();
    newAuthor.FirstName = firstName.Text;
    newAuthor.LastName = lastName.Text;
    newAuthor.AuthodSSID = 20;
    newAuthor.AuthorID = 10
//Check if record exist here
    publishContext.AddToAuthor(newAuthor);//insert if does not exist

}

解决方案

The only way to check if a record exists is to query the record and see if anything comes back:

var existingAuthorCount = publishContext.Author.Count(a => a.AuthodSSID == 20);
if (existingAuthorCount == 0) 
{
    // Do your insert
}

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