使用DbSet应用OrderBy [英] Apply OrderBy with DbSet
本文介绍了使用DbSet应用OrderBy的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!
问题描述
我想实现分页,并与通用存储库进行排序。 ?如何采取主键列默认顺序由列DbSet
DbSet = Context.Set< T>();
公众的IQueryable< T> GETALL(INT PAGENUMBER = 0,INT的pageSize = 10,串sortColumn =)
{
返回DbSet.OrderBy(如何在这里使用的主键列)。跳过(PAGENUMBER * pageSize的)取(pageSize的);
}
解决方案
我已经使用了这些扩展方法实现类似的东西:
公共静态字符串GetKeyField(type类型)
{
VAR allProperties =类型.GetProperties();
VAR keyProperty = allProperties.SingleOrDefault(P => p.IsDefined(typeof运算(KeyAttribute)));
返回keyProperty!= NULL? keyProperty.Name:空;
}
公共静态的IQueryable< T>排序依据< T>(这IQueryable的< T>源,串排序依据)
{
返回source.GetOrderByQuery(排序依据,排序依据);
}
公共静态的IQueryable< T> OrderByDescending< T>(这IQueryable的< T>源,串排序依据)
{
返回source.GetOrderByQuery(排序依据,OrderByDescending);
}
私有静态的IQueryable< T> GetOrderByQuery< T>(这IQueryable的< T>源,串排序依据,字符串methodName中)
{
VAR sourceType的= typeof运算(T);
VAR财产= sourceType.GetProperty(排序依据);
变种parameterExpression = Expression.Parameter(sourceType的,X);
VAR getPropertyExpression = Expression.MakeMemberAccess(parameterExpression,属性);
VAR orderByExpression = Expression.Lambda(getPropertyExpression,parameterExpression);
VAR resultExpression = Expression.Call(typeof运算(可查询),方法名,
新的[] {sourceType的,property.PropertyType},source.Expression,
orderByExpression);
返回source.Provider.CreateQuery< T>(resultExpression);
}
这允许你通过属性名作为一个字符串,并建立一个表达它传递到正规的LINQ的OrderBy()函数。所以你的情况,使用情况将是:
DbSet = Context.Set< T>();
公众的IQueryable< T> GETALL(INT PAGENUMBER = 0,INT的pageSize = 10,串sortColumn =)
{
返回DbSet.OrderBy(GetKeyField(typeof运算(T)))跳过(PAGENUMBER * pageSize的)采取(pageSize的);
}
这假定您的关键领域中的实体类装饰正确地与键
属性。
I am trying to implement pagination and sorting with generic repository. How to take primary key column as default order by column in DbSet ?
DbSet = Context.Set<T>();
public IQueryable<T> GetAll(int pageNumber = 0, int pageSize = 10, string sortColumn = "")
{
return DbSet.OrderBy("how to use primary key column here").Skip(pageNumber * pageSize)Take(pageSize);
}
解决方案
I have used these extension methods to achieve something similar:
public static string GetKeyField(Type type)
{
var allProperties = type.GetProperties();
var keyProperty = allProperties.SingleOrDefault(p => p.IsDefined(typeof(KeyAttribute)));
return keyProperty != null ? keyProperty.Name : null;
}
public static IQueryable<T> OrderBy<T>(this IQueryable<T> source, string orderBy)
{
return source.GetOrderByQuery(orderBy, "OrderBy");
}
public static IQueryable<T> OrderByDescending<T>(this IQueryable<T> source, string orderBy)
{
return source.GetOrderByQuery(orderBy, "OrderByDescending");
}
private static IQueryable<T> GetOrderByQuery<T>(this IQueryable<T> source, string orderBy, string methodName)
{
var sourceType = typeof(T);
var property = sourceType.GetProperty(orderBy);
var parameterExpression = Expression.Parameter(sourceType, "x");
var getPropertyExpression = Expression.MakeMemberAccess(parameterExpression, property);
var orderByExpression = Expression.Lambda(getPropertyExpression, parameterExpression);
var resultExpression = Expression.Call(typeof(Queryable), methodName,
new[] { sourceType, property.PropertyType }, source.Expression,
orderByExpression);
return source.Provider.CreateQuery<T>(resultExpression);
}
This allows you to pass the property name as a string and build up an expression which it passes to the regular LINQ OrderBy() function. So in your case, the usage would be:
DbSet = Context.Set<T>();
public IQueryable<T> GetAll(int pageNumber = 0, int pageSize = 10, string sortColumn = "")
{
return DbSet.OrderBy(GetKeyField(typeof(T))).Skip(pageNumber * pageSize)Take(pageSize);
}
This assumes your key field in your entity class is properly decorated with the Key
attribute.
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