如何使用linq获取数据 [英] How to get data using linq

问题描述

这是我的DAL功能。

This is my DAL function.

public IQueryable GetAllCategories()
        {
            CastroDataContext objDAL = new CastroDataContext();

            var varCategories = (from cat in objDAL.Categories
                                 where cat.IsDeleted.Equals(false)
                                 select new
                                 {
                                     CategoryID = this.ToInteger(cat.CategoryID),
                                     CategoryName = this.ToString(cat.CategoryName),
                                     Description = this.ToString(cat.Description),
                                     EvaluationType = this.ToString(cat.EvaluationType),
                                 });


            return varCategories;
        }

我想知道如何在我的组合框中获取数据。



i我正在尝试这个

and i want to know that how to get the data at my front end in my combobox.

i am trying this

protected void GetCategories()
        {            
            clsCategories DAL = new clsCategories();
            IQueryable ds = DAL.GetAllCategories();
            CastroDataContext db = new CastroDataContext();
            var query = from category in db.Categories select category;
                      
            foreach (var row in query)
            {
            
            }
}

但是这里是error.plz guaid me

But here are error.plz guaid me

推荐答案

大部分如果不是你的所有问题都在 GetCategories（）



为什么你在DAL中运行查询然后尝试在GetCategories方法中执行相同操作？



我首先检查以确保 ds 变量在运行该例程时其中包含数据（以防万一你怎么办？在该行上放置一个断点） ，跳过它并通过调试器查看返回的内容。



如果返回记录，则可以执行此类操作

Mostly if not ALL of your problem is in GetCategories()

Why are you running a query in your DAL and then trying to do the same in your GetCategories method?

I would firstly check to make sure that the ds variable has data inside of it when you run that routine (just in case you ask how? put a breakpoint on that line, step over it and through the debugger see what gets returned).

If that returns records, you can then do something like this

 foreach(var row in ds)
 {
   //Do something to your data here
   //i.e. 
   int CategoryID = row.CategoryID;
 }


hopefully this should give you something to get started with.

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