首先感谢园子里的“红烧狮子头”，他的工作是本文的基础,引文如下http://www.cnblogs.com/daviddai/archive/2013/03/09/2952087.html,本版本实现了类似SQL中的like与in的功能，实现了多orderby的级联排序，下面贴出代码:
一些辅助类:
public enum ConditionFlags
{
And = ,
Or = ,
} public enum RelationFlags
{
Equal = ,
NoEqual = ,
GreaterThan = ,
LessThan = ,
GreaterThanOrEqual = ,
LessThanOrEqual = ,
LikeWildcardBoth = ,
LikeLeftWildcardOnly = ,
LikeRightWildcardOnly = ,
In = ,
} public class QueryCondition
{
public string ConditionField { get; set; }
public object FieldValue { get; set; }
public ConditionFlags Condition { get; set; }
public RelationFlags Relation { get; set; }
} public class OrderByCondition
{
public string OrderField { get; set; }
public bool IsDesc { get; set; }
}
实现IEnumerable的实现方法:
public static IEnumerable<T> GetDataByDynamicQuery<T>(this IEnumerable<T> sourceList, List<QueryCondition> queryConditionList, params OrderByCondition[] orderByConditionList)
{
if (null == sourceList)
{
throw new ArgumentException("source list must not be null");
} IQueryable<T> sourceLs = sourceList.AsQueryable(); Expression finalExpr;
Expression filter, totalExpr;
filter = totalExpr = Expression.Constant(true); ParameterExpression param = Expression.Parameter(typeof(T), "n");
foreach (var item in queryConditionList ?? Enumerable.Empty<QueryCondition>())
{
//反射找出所有查询条件的属性值，如果该查询条件值为空或者null不添加动态lambda表达式
string propertyName = item.ConditionField;
var propertyVal = item.FieldValue; if (!string.IsNullOrEmpty(propertyName) && propertyVal != null && propertyVal.ToString() != string.Empty)
{
//n.property
PropertyInfo property = typeof(T).GetProperty(propertyName);
Expression left = Expression.Property(param, property);
//等式右边的值
Expression right = Expression.Constant(propertyVal);
MethodInfo containsmethod;
switch (item.Relation)
{
case RelationFlags.Equal:
if (typeof(string) == property.PropertyType)
{
containsmethod = typeof(string).GetMethod("Equals", new[] { typeof(string), typeof(string), typeof(StringComparison) }); filter = Expression.Call(containsmethod,left, right, Expression.Constant(StringComparison.OrdinalIgnoreCase));
}
else
{
filter = Expression.Equal(left, right);
}
break;
case RelationFlags.NoEqual:
filter = Expression.NotEqual(left, right);
break;
case RelationFlags.GreaterThan:
filter = Expression.GreaterThan(left, right);
break;
case RelationFlags.LessThan:
filter = Expression.LessThan(left, right);
break;
case RelationFlags.GreaterThanOrEqual:
filter = Expression.GreaterThanOrEqual(left, right);
break;
case RelationFlags.LessThanOrEqual:
filter = Expression.LessThanOrEqual(left, right);
break;
case RelationFlags.LikeWildcardBoth:
if (typeof (string) == property.PropertyType)
{
containsmethod = property.PropertyType.GetMethod("Contains", new Type[] { property.PropertyType });
filter = Expression.Call(left, containsmethod, right);
}
else
{
throw new ArgumentException(" 'like %x%' operator work on string type only ");
}
break;
case RelationFlags.LikeLeftWildcardOnly:
if (typeof (string) == property.PropertyType)
{
containsmethod = property.PropertyType.GetMethod("EndsWith", new Type[] { property.PropertyType });
filter = Expression.Call(left, containsmethod, right);
}
else
{
throw new ArgumentException(" 'like %x' operator work on string type only ");
}
break;
case RelationFlags.LikeRightWildcardOnly:
if (typeof (string) == property.PropertyType)
{
containsmethod = property.PropertyType.GetMethod("StartsWith", new Type[] { property.PropertyType });
filter = Expression.Call(left, containsmethod, right);
}
else
{
throw new ArgumentException(" 'like x%' operator work on string type only ");
}
break;
case RelationFlags.In:
Expression rightTmp, filterTmp;
Expression totalExprTmp = Expression.Constant(false);
foreach (var itemValue in propertyVal as IEnumerable ?? Enumerable.Empty<object>())
{
rightTmp = Expression.Constant(itemValue);
if (typeof(string) == property.PropertyType)
{
containsmethod = typeof(string).GetMethod("Equals", new[] { typeof(string), typeof(string), typeof(StringComparison) });
filterTmp = Expression.Call(containsmethod,left, rightTmp, Expression.Constant(StringComparison.OrdinalIgnoreCase));
}
else
{
filterTmp = Expression.Equal(left, rightTmp);
}
totalExprTmp = Expression.Or(filterTmp, totalExprTmp);
}
filter = totalExprTmp = Expression.And(totalExprTmp, Expression.Constant(true));
break;
default:
filter = Expression.Constant(true);
break;
}
switch (item.Condition)
{
case ConditionFlags.And:
totalExpr = Expression.And(totalExpr, filter);
break;
case ConditionFlags.Or:
totalExpr = Expression.Or(totalExpr.NodeType.Equals(Expression.Constant(true).NodeType) ? Expression.Constant(false) : totalExpr, filter);
break;
default:
break;
}
}
}
//Where部分条件
Expression pred = Expression.Lambda(totalExpr, param);
finalExpr = Expression.Call(typeof(Queryable), "Where", new Type[] { typeof(T) }, Expression.Constant(sourceLs), pred);
string orderByFunctionName = "OrderBy";
string orderByDescFunctionName = "OrderByDescending";
foreach (var orderbyCondition in orderByConditionList ?? Enumerable.Empty<OrderByCondition>())
{
PropertyInfo pInfo = typeof(T).GetProperty(orderbyCondition.OrderField);
//OrderBy部分排序
finalExpr = Expression.Call(typeof(Queryable), orderbyCondition.IsDesc ? orderByDescFunctionName : orderByFunctionName, new Type[] { typeof(T), pInfo.PropertyType }, finalExpr, Expression.Lambda(Expression.Property(param, pInfo), param));
orderByFunctionName = "ThenBy";
orderByDescFunctionName = "ThenByDescending";
} return sourceLs.Provider.CreateQuery<T>(finalExpr);
}
调用示例:
if (queryEntity.ApplicationIds != null && queryEntity.ApplicationIds.Length > )
{
var queryCondition = new QueryCondition
{
ConditionField = "ApplicationId",
FieldValue = queryEntity.ApplicationIds,
Condition = ConditionFlags.And,
Relation = RelationFlags.In
};
queryConditionList.Add(queryCondition);
}
if (!string.IsNullOrWhiteSpace(queryEntity.LinkPath))
{
var queryCondition = new QueryCondition();
queryCondition.ConditionField = "LinkPath";
queryCondition.FieldValue = queryEntity.LinkPath;
queryCondition.Condition = ConditionFlags.And;
queryCondition.Relation = RelationFlags.Equal;
queryConditionList.Add(queryCondition);
}
var orderByConditionList = new List<OrderByCondition>();
var orderByCondition = new OrderByCondition {OrderField = "SortIndex", IsDesc = true};
orderByConditionList.Add(orderByCondition);
var orderByConditionMenuId = new OrderByCondition {OrderField = "MenuId", IsDesc = false};
orderByConditionList.Add(orderByConditionMenuId);
return alllist.GetDataByDynamicQuery<ControlPanelMenuEntity>(queryConditionList, orderByConditionList.ToArray()).ToList();