/// <summary>
/// 把查询参数转换成表达式目录树
/// </summary>
/// <typeparam name="T"></typeparam>
/// <param name="queryParam"></param>
/// <returns></returns>
public static Expression <Func <T, bool> > QueryParamToExpression <T>(this QueryParam queryParam)
{
ParameterExpression parameterExpression = Expression.Parameter(typeof(T), "a");
Expression member = EntityHelper <T> .GetMemberExpression(parameterExpression, queryParam.Field);
if (member == null)
{
return(null);
}
//获取当前属性的类型
Type memberType = member.Type;
object constantValue = null;
//当前传入值的类型（实际查询的类型）
Type valueType = memberType.IsNullableType() ? memberType.GetGenericArguments().First() : memberType;
//int类型转double查询
if (valueType == typeof(int))
{
valueType = typeof(double);
}
//把查询的值转换为对应的值
constantValue = DataUtils.ChangeType(queryParam.Value, valueType);
Expression constant = Expression.Constant(constantValue, valueType);
//把参数类型转换一下
constant = Expression.Convert(constant, memberType);
Expression <Func <T, bool> > where = null;
switch (queryParam.Logic)
{
//等于
case Common.Core.LogicEnum.Equal:
return(Expression.Lambda <Func <T, bool> >(Expression.Equal(member, constant), parameterExpression));
//包含 右包含 左包含
case Common.Core.LogicEnum.Like:
case Common.Core.LogicEnum.NoLike:
case Common.Core.LogicEnum.LikeLeft: //右包含
case Common.Core.LogicEnum.LikeRight: //左包含
{
var method = queryParam.Logic.ToMethod();
Expression mehtodCallExpression = Expression.Call(member, method, constant);
// mehtodCallExpression.Not()
where = Expression.Lambda <Func <T, bool> >(mehtodCallExpression, parameterExpression);
if (queryParam.Logic == Common.Core.LogicEnum.NoLike)
{
where = where.Not();
}
return(where);
}
//大于
case Common.Core.LogicEnum.GreaterThan:
return(Expression.Lambda <Func <T, bool> >(Expression.GreaterThan(member, constant), parameterExpression));
//大于等于
case Common.Core.LogicEnum.GreaterThanOrEqual:
return(Expression.Lambda <Func <T, bool> >(Expression.GreaterThanOrEqual(member, constant), parameterExpression));
//少于
case Common.Core.LogicEnum.LessThan:
return(Expression.Lambda <Func <T, bool> >(Expression.LessThan(member, constant), parameterExpression));
//少于等于
case Common.Core.LogicEnum.LessThanOrEqual:
return(Expression.Lambda <Func <T, bool> >(Expression.LessThanOrEqual(member, constant), parameterExpression));
//
case Common.Core.LogicEnum.In:
break;
case Common.Core.LogicEnum.NotIn:
break;
//不等于
case Common.Core.LogicEnum.NoEqual:
return(Expression.Lambda <Func <T, bool> >(Expression.NotEqual(member, constant), parameterExpression));
case Common.Core.LogicEnum.IsNullOrEmpty:
break;
case Common.Core.LogicEnum.IsNot:
break;
}
return(null);
}
