IQueryable的列出< T> [英] IQueryable to List<T>

问题描述

我知道的IQueryable产生任何结果，但只是一个表达式生成器，我的问题其实是如何使用它来执行查询并返回一组排列方式要能够把它绑定在一个网格。

I know IQueryable yields no result but just an expression builder, my problem is how can actually use it to execute query and return the set as List to be able to bind it on a grid.

  IQueryable query = _campaignManager.GetCampaign(filter, values);

  // this line returns error
  List<Campaign> campaigns = query.Cast<Campaign>().ToList();

  grdCampaigns.DataSource = campaigns;
  grdCampaigns.DataBind();

其他详细信息：GetCampaign（）

additional details: GetCampaign()

    public IQueryable GetCampaign(string filter, params object[] values)
    {
        string parameters = string.Empty;
        foreach (object obj in values)
        {
            parameters += obj.ToString() + ",";
        }

        parameters.Remove(parameters.Count() - 1, 1);

        var query = context.Campaigns.Where(filter, parameters)
           .Select("new(CampaignID,CampaignName)");

        return query;
    }

我使用的 DynamicQueryable 动态LINQ查询

DynamicQueryable

The .Select Extension method of the DynamicQueryable

     public static IQueryable Select(this IQueryable source, string selector, params object[] values)
    {
        if (source == null) throw new ArgumentNullException("source");
        if (selector == null) throw new ArgumentNullException("selector");
        LambdaExpression lambda = DynamicExpression.ParseLambda(source.ElementType, null, selector, values);
        return source.Provider.CreateQuery(
            Expression.Call(
                typeof(Queryable), "Select",
                new Type[] { source.ElementType, lambda.Body.Type },
                source.Expression, Expression.Quote(lambda)));
    }

IQueryable的。凡（）扩展

IQueryable .Where() extension

       public static IQueryable Where(this IQueryable source, string predicate, params object[] values)
    {
        if (source == null) throw new ArgumentNullException("source");
        if (predicate == null) throw new ArgumentNullException("predicate");
        LambdaExpression lambda = DynamicExpression.ParseLambda(source.ElementType, typeof(bool), predicate, values);
        return source.Provider.CreateQuery(
            Expression.Call(
                typeof(Queryable), "Where",
                new Type[] { source.ElementType },
                source.Expression, Expression.Quote(lambda)));
    }

感谢...

thanks...

推荐答案

的IQueryable可以是T型的EG
的IQueryable查询= + CampaignManager.GetCampaign

IQueryable can be of type T e.g. IQueryable query=+CampaignManager.GetCampaign

但由于您使用的IQueryable可以使用

but since you are using IQueryable you can use

var enumerator= c.GetEnumerator();
            while (enumerator.MoveNext())
            {
             //add these records to some collection say Collection or Campaign or Create any entity with Name and Id and then assign that collection to DataSource    
            }

我已经试过了它的工作就可以继续机智。

i have tried that it's working you can proceed wit it.

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