Linq 通过反射动态查询对象

public IQueryable<TEntity> Find<TEntity>(TEntity obj) where TEntity : class
        
{
            
//获得所有property的信息
            PropertyInfo[] properties = obj.GetType().GetProperties(BindingFlags.Public |
 BindingFlags.Instance);
            
//构造初始的query
            IQueryable<TEntity> query = this.GetTable<TEntity>().AsQueryable<TEntity>();
            
//遍历每个property
            foreach (PropertyInfo p in properties)
            
{
                
if (p != null)
                
{
                    Type t 
= p.PropertyType;
                    
//加入object,Binary,和XDocument, 支持sql_variant,imager 和xml等的影射。
                    if (t.IsValueType || t == typeof(string|| t == typeof(System.Byte[])
                        
|| t == typeof(object|| t == typeof(System.Xml.Linq.XDocument)
                        
|| t == typeof(System.Data.Linq.Binary))
                    
{
                        
//如果不为null才算做条件
                        if ( p.GetValue(obj, null!= null)
                        
{
                            ParameterExpression param 
= Expression.Parameter(typeof(TEntity), "c");
                            Expression right 
= Expression.Constant(p.GetValue(obj, null));
                            Expression left 
= Expression.Property(param, p.Name);
                            Expression filter 
= Expression.Equal(left,right);

                            Expression
<Func<TEntity, bool>> pred = Expression.Lambda<Func
<
TEntity, bool>>(filter, param);
                            query 
= query.Where(pred);
                        }

                    }

                }

            }

            
return query;
        }

 

调用:

            Customer c = new Customer();
            c.City 
= "London";
            c.Phone 
= "23236133";

            var q 
= db.Find<Customer>(c).ToList();


posted @ 2008-12-25 15:20  昕友软件开发  阅读(863)  评论(0编辑  收藏  举报
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