实体框架中的返回值 [英] Return value in entity framework

问题描述

我尝试使用下拉值在高级图表中显示数据代码



我尝试过：

i try this code for display data in high charts using dropdown value

What I have tried:

[WebMethod]
public static string jqufunc(int year)
{

    string res = "[";
    ProjectdbEntities a = new ProjectdbEntities();

    var b = a.Catg_type;

    foreach (var c in b)
    {

        res += "'" + c.Catg_type1 + "',";
    }
    res = res.Substring(0, res.Length - 1);
    res += "]";

   


    //for program type
    var allprogs = a.Program_type;
    string res2 = "[";
    foreach (var pr in allprogs)
    {
        res2 += "{name: '" + pr.Prog_name + "',";


        string res3 = "[";
        var y = a.Year_info;
        foreach (var g in y)
        {
            res3 += "'" + g.year + "',";

            //for category type
            var allcats = a.Catg_type;

            res2 += "data:[";

            foreach (var ct in allcats)
            {
                res2 += a.Std_info.Where(t => t.Catg_id == ct.Catg_id && t.Prog_id == pr.Prog_id && t.year_id==g.year_id).Count().ToString().ToList() + ",";

            }

            res2 = res2.Substring(0, res2.Length - 1);
            res2 += "]";
            res2 += "},";



        }
        res2 = res2.Substring(0, res2.Length - 1);
        res2 += "]";
        //return (from c in a.Year_info where c.year_id == year select c).ToList();
        return res + "*" + res2;

    }
}

但显示错误



'WebApplication1.WebForm1.jqufunc（int）'：并非所有代码路径都返回一个值

i已经返回一个值



任何解决方案

but this shows error

'WebApplication1.WebForm1.jqufunc(int)': not all code paths return a value
i already return a value

any solution

推荐答案

您的代码 - 过度简化：

Your code - over-simplified:

[WebMethod]
public static string jqufunc(int year)
{
    foreach (var pr in allprogs)
    {
        return res + "*" + res2;
    }
}

您可以看到此代码仅在时返回任何内容allprogs 至少有一个成员 - 而且不会承诺...

如果没有成员，代码将永远不会进入 foreach 并且不会点击返回 ...

You can see that this code will return anything only if allprogs has at least one member - and that's not promised nowhere...
If there are no members the code will never enter the foreach and will not hit the return...

我们不知道你的代码背后的逻辑，似乎很多循环是否有



return 关键字应该放在循环之外，因为你要返回一些值。



在函数的最后一行返回变量（res）。



始终遵循此模式

We dont know about the logic behind your code, seems lot of looping are there

the return keyword should be placed outside the loop since you are returning some value.

return the variable (res) at the last line of the function.

always follow this pattern

public  ReturnType  MyMethod()
       {
            ReturnType  returnValue = default(ReturnType);
           //
           // Your Code (for loop or any )
           //
           return returnValue;
       }

这篇关于实体框架中的返回值的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！