错误:"TEntity"类型必须是引用类型

Question

public partial class GridMastercontrol<TEntity> : UserControl
{
private System.Data.Objects.ObjectSet<TEntity> _osMain; // error here
}

我无法声明泛型类型的对象集.请帮我怎么做.

错误消息是 - 'TEntity'类型必须是引用类型才能在泛型类型或方法'System.Data.Objects.ObjectSet'中将其用作参数'TEntity'

Answer 1

将通用约束添加到类声明中:

public partial class GridMastercontrol<TEntity> : UserControl where TEntity : class

你必须这样做,因为ObjectSet<TEntity>已经有一个:

public class ObjectSet<TEntity> : ObjectQuery<TEntity>, 
        IObjectSet<TEntity>, IQueryable<TEntity>, IEnumerable<TEntity>, 
        IQueryable, IEnumerable
where TEntity : class