Entity Framework 在OrderBy排序中使用字符串

Posted on 2021-04-14 20:22 火冰·瓶阅读(256) 评论(0) 编辑收藏举报

public static class LinqExtensions
{
    private static PropertyInfo GetPropertyInfo(Type objType, string name)
    {
        var properties = objType.GetProperties();
        var matchedProperty = properties.FirstOrDefault(p => p.Name == name);
        if (matchedProperty == null)
            throw new ArgumentException("name");
 
        return matchedProperty;
    }
    private static LambdaExpression GetOrderExpression(Type objType, PropertyInfo pi)
    {
        var paramExpr = Expression.Parameter(objType);
        var propAccess = Expression.PropertyOrField(paramExpr, pi.Name);
        var expr = Expression.Lambda(propAccess, paramExpr);
        return expr;
    }
 
    public static IEnumerable<T> OrderBy<T>(this IEnumerable<T> query, string name)
    {
        var propInfo = GetPropertyInfo(typeof(T), name);
        var expr = GetOrderExpression(typeof(T), propInfo);
 
        var method = typeof(Enumerable).GetMethods().FirstOrDefault(m => m.Name == "OrderBy" && m.GetParameters().Length == 2);
        var genericMethod = method.MakeGenericMethod(typeof(T), propInfo.PropertyType);
        return (IEnumerable<T>)genericMethod.Invoke(null, new object[] { query, expr.Compile() });
    }
 
    public static IQueryable<T> OrderBy<T>(this IQueryable<T> query, string name)
    {
        var propInfo = GetPropertyInfo(typeof(T), name);
        var expr = GetOrderExpression(typeof(T), propInfo);
 
        var method = typeof(Queryable).GetMethods().FirstOrDefault(m => m.Name == "OrderBy" && m.GetParameters().Length == 2);
        var genericMethod = method.MakeGenericMethod(typeof(T), propInfo.PropertyType);
        return (IQueryable<T>)genericMethod.Invoke(null, new object[] { query, expr });
    }
 
 
 
    public static IEnumerable<T> OrderByDescending<T>(this IEnumerable<T> query, string name)
    {
        var propInfo = GetPropertyInfo(typeof(T), name);
        var expr = GetOrderExpression(typeof(T), propInfo);
 
        var method = typeof(Enumerable).GetMethods().FirstOrDefault(m => m.Name == "OrderByDescending" && m.GetParameters().Length == 2);
        var genericMethod = method.MakeGenericMethod(typeof(T), propInfo.PropertyType);
        return (IEnumerable<T>)genericMethod.Invoke(null, new object[] { query, expr.Compile() });
    }
 
    public static IQueryable<T> OrderByDescending<T>(this IQueryable<T> query, string name)
    {
        var propInfo = GetPropertyInfo(typeof(T), name);
        var expr = GetOrderExpression(typeof(T), propInfo);
 
        var method = typeof(Queryable).GetMethods().FirstOrDefault(m => m.Name == "OrderByDescending" && m.GetParameters().Length == 2);
        var genericMethod = method.MakeGenericMethod(typeof(T), propInfo.PropertyType);
        return (IQueryable<T>)genericMethod.Invoke(null, new object[] { query, expr });
    }
}

基础

//常规方法
var query = s.OrderBy(x =>x.Age);
 
 
//排序
s.OrderBy(x => GetPropertyValue(x, "Age"))
 
//函数支持
private static object GetPropertyValue(object obj, string property)
{
    PropertyInfo propertyInfo = obj.GetType().GetProperty(property);
    return propertyInfo.GetValue(obj, null);
} 