Linq 联合条件查询快捷方法

原方法：

public ProductDC[] GetProductQueryCondition(ProductQueryConditionDC filter)
{//红色为原来的联合条件（之后下面的修改过的方法是使用了，相关的条件联合方法）

var datas = Repository.LoadEntities<Product>(o => o.Status != (int)ProductStatus.Disabled
&& ((!string.IsNullOrEmpty(filter.ProductNo) && (o.ProductNo.Contains(filter.ProductNo)))
|| (!string.IsNullOrEmpty(filter.ProductName) && (o.ProductNo.Contains(filter.ProductName)))
|| ((filter.Category == (int)ProductCategory.All ? (new int?[] { (int)ProductCategory.FinishedProduct, (int)ProductCategory.SemiFinishedProduct }).Contains(o.Category) : o.Category == filter.Category))
|| ((filter.Status == (int)ProductStatus.All ? (new int?[] { (int)ProductStatus.Building, (int)ProductStatus.SignIn, (int)ProductStatus.TobeReleased, (int)ProductStatus.Released }).Contains(o.Status) : o.Status == filter.Status))
|| (!string.IsNullOrEmpty(filter.Customer) && (o.ProductNo.Contains(filter.Customer)))
|| ((filter.StartDate != null ? (filter.EndDate != null ? (o.MkDate > filter.StartDate && o.MkDate < filter.EndDate) : o.MkDate > filter.StartDate) : (filter.EndDate != null ? o.MkDate < filter.EndDate : o.MkDate == o.MkDate)))))
.Select(p => new ProductDC()
{
ProductId = p.ProductId,
ProductNo = p.ProductNo,
ProductName = p.ProductName,
Ver = p.Ver,
Spec = p.Spec,
Customer = p.Customer,
Category = p.Category,
CategoryName = p.Category == (int)ProductCategory.FinishedProduct ? "成品" : p.Category == (int)ProductCategory.SemiFinishedProduct ? "半成品" : "",
Status = p.Status,
StatusName = p.Status == (int)ProductStatus.Building ? "新建中" : p.Status == (int)ProductStatus.SignIn ? "会签中" : p.Status == (int)ProductStatus.TobeReleased ? "待发布" : p.Status == (int)ProductStatus.Released ? "已发布" : p.Status == (int)ProductStatus.Disabled ? "已停用" : "",
Description = p.Description,
Other1 = p.Other1,
Other2 = p.Other2,
Other3 = p.Other3,
Other4 = p.Other4,
MkUserId = p.MkUserId,
MkDate = p.MkDate,
CountersignCode = p.CountersignCode,
Pubdate = p.Pubdate,
Stopdate = p.Stopdate
});
return datas.ToArray();}

方法：

public ProductDC[] GetProductQueryCondition(ProductQueryConditionDC filter)
{

var Predicate = PredicateBuilder.True<Product>();//PredicateBuilder是下面红色标记的条件联合类

Predicate = Predicate.And<Product>(x => x.Status != (int)ProductStatus.Disabled);
if (!string.IsNullOrWhiteSpace(filter.ProductNo))
{
Predicate = Predicate.And<Product>(x => x.ProductNo.Contains(filter.ProductNo));
}
if (!string.IsNullOrWhiteSpace(filter.ProductName))
{
Predicate = Predicate.And<Product>(x => x.ProductName.Contains(filter.ProductName));
}
if (filter.Category == (int)ProductCategory.All)
{
Predicate = Predicate.And<Product>(x => new int?[] { (int)ProductCategory.FinishedProduct, (int)ProductCategory.SemiFinishedProduct }.Contains(x.Category));
}
else
{
Predicate = Predicate.And<Product>(x => x.Category == filter.Category);
}
if (filter.Status == (int)ProductStatus.All)
{
Predicate = Predicate.And<Product>(x => new int?[] { (int)ProductStatus.Building, (int)ProductStatus.SignIn, (int)ProductStatus.TobeReleased, (int)ProductStatus.Released }.Contains(x.Status));
}
else
{
Predicate = Predicate.And<Product>(x => x.Status == filter.Status);
}
if (!string.IsNullOrWhiteSpace(filter.Customer))
{
Predicate = Predicate.And<Product>(x => x.Customer.Contains(filter.Customer));
}
if (filter.StartDate.HasValue)
{
Predicate = Predicate.And<Product>(x => x.MkDate > filter.StartDate.GetValueOrDefault());
}
if (filter.EndDate.HasValue)
{
Predicate = Predicate.And<Product>(x => x.MkDate < filter.EndDate.GetValueOrDefault());
}

var datas = Repository.LoadEntities<Product>(Predicate)
.Select(p => new ProductDC()
{
ProductId = p.ProductId,
ProductNo = p.ProductNo,
ProductName = p.ProductName,
Ver = p.Ver,
Spec = p.Spec,
Customer = p.Customer,
Category = p.Category,
CategoryName = p.Category == (int)ProductCategory.FinishedProduct ? "成品" : p.Category == (int)ProductCategory.SemiFinishedProduct ? "半成品" : "",
Status = p.Status,
StatusName = p.Status == (int)ProductStatus.Building ? "新建中" : p.Status == (int)ProductStatus.SignIn ? "会签中" : p.Status == (int)ProductStatus.TobeReleased ? "待发布" : p.Status == (int)ProductStatus.Released ? "已发布" : p.Status == (int)ProductStatus.Disabled ? "已停用" : "",
Description = p.Description,
Other1 = p.Other1,
Other2 = p.Other2,
Other3 = p.Other3,
Other4 = p.Other4,
MkUserId = p.MkUserId,
MkDate = p.MkDate,
CountersignCode = p.CountersignCode,
Pubdate = p.Pubdate,
Stopdate = p.Stopdate
});
return datas.ToArray();
}

使用的条件联合的类

#region PredicateBuilder
public static class PredicateBuilder
{

/// <summary>
/// 机关函数应用False时：单个AND无效，多个AND无效；单个OR有效，多个OR有效；混应时写在OR后面的AND有效
/// </summary>
/// <typeparam name="T"></typeparam>
/// <returns></returns>
public static Expression<Func<T, bool>> True<T>() { return f => true; }

/// <summary>
/// 机关函数应用True时：单个AND有效，多个AND有效；单个OR无效，多个OR无效；混应时写在AND后的OR有效
/// </summary>
/// <typeparam name="T"></typeparam>
/// <returns></returns>
public static Expression<Func<T, bool>> False<T>() { return f => false; }
public static Expression<T> Compose<T>(this Expression<T> first, Expression<T> second, Func<Expression, Expression, Expression> merge)
{
// build parameter map (from parameters of second to parameters of first)
var map = first.Parameters.Select((f, i) => new { f, s = second.Parameters[i] }).ToDictionary(p => p.s, p => p.f);
// replace parameters in the second lambda expression with parameters from the first
var secondBody = ParameterRebinder.ReplaceParameters(map, second.Body);
// apply composition of lambda expression bodies to parameters from the first expression
return Expression.Lambda<T>(merge(first.Body, secondBody), first.Parameters);
}
public static Expression<Func<T, bool>> And<T>(this Expression<Func<T, bool>> first, Expression<Func<T, bool>> second)
{
return first.Compose(second, Expression.And);
}
public static Expression<Func<T, bool>> Or<T>(this Expression<Func<T, bool>> first, Expression<Func<T, bool>> second)
{
return first.Compose(second, Expression.Or);
}
}
public class ParameterRebinder : ExpressionVisitor
{
private readonly Dictionary<ParameterExpression, ParameterExpression> _map;
public ParameterRebinder(Dictionary<ParameterExpression, ParameterExpression> map)
{
_map = map ?? new Dictionary<ParameterExpression, ParameterExpression>();
}
public static Expression ReplaceParameters(Dictionary<ParameterExpression, ParameterExpression> map, Expression exp)
{
return new ParameterRebinder(map).Visit(exp);
}
protected override Expression VisitParameter(ParameterExpression p)
{
ParameterExpression replacement;
if (_map.TryGetValue(p, out replacement))
{
p = replacement;
}
return base.VisitParameter(p);
}
}