LINQ to SQL insert-if-non-existent

作者: 日天大圣
来源: 51数据库
2022-12-08

问题描述

如果表中不存在记录，我想知道是否有更简单的方法来插入记录.我仍在努力培养我的 LINQ to SQL 技能.

I'd like to know if there's an easier way to insert a record if it doesn't already exist in a table. I'm still trying to build my LINQ to SQL skills.

这是我所知道的，但似乎应该有更简单的方法.

Here's what I've got, but it seems like there should be an easier way.

public static TEntity InsertIfNotExists<TEntity>
(
    DataContext db,
    Table<TEntity> table,
    Func<TEntity,bool> where,
    TEntity record
)
    where TEntity : class
{
    TEntity existing = table.SingleOrDefault<TEntity>(where);

    if (existing != null)
    {
        return existing; 
    }
    else
    {
        table.InsertOnSubmit(record);

        // Can't use table.Context.SubmitChanges()
        // 'cause it's read-only

        db.SubmitChanges();
    }

    return record;
}

推荐答案

public static void InsertIfNotExists<TEntity>
                    (this Table<TEntity> table,
                     TEntity entity,
                     Expression<Func<TEntity,bool>> predicate)
    where TEntity : class
{ 
    if (!table.Any(predicate)) 
    {
        table.InsertOnSubmit(record);
        table.Context.SubmitChanges();
    }
 }


table.InsertIfNotExists(entity, e=>e.BooleanProperty);

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