如何检查Linq查询结果中的DBNull值 [英] How to check DBNull value in Linq query results

问题描述

我正在使用以下代码，并尝试按货币和代码分组。之后，我试图循环结果集。

I am using the below code and trying to group by Currency and Code. After this I am trying to loop through the result set.

但问题是循环结果，最后我得到以下每个异常语句：

But the issue is while looping through the results, at the end I am getting the below exception on the for each statement:

对象不能从DBNull转换为其他类型。

    DataTable dt = new DataTable();

    var result = from r in dt.AsEnumerable()
               result r by new
               {
                    currency = r.Field<String>("CURRENCY"),
                    Code = r.Field<String>("CODE")
               }
              into grp
              select new
              {
                   currency = grp.Key.currency,
                   Code = grp.Key.Code,
                   amount = grp.Sum(x => Convert.ToDouble(x["AMOUNT"]))
              };

    foreach (var obj in result)
    {
      String sCurr =obj.currency;
      String Code = obj.Code;
      string amount= obj.amount.ToString());
    }

请帮助我解决这个问题。

Please help me to resolve this issue.

推荐答案

像

 amount = grp.Sum(x => Convert.ToDouble(x["AMOUNT"] == DBNull.Value ? 0 : x["AMOUNT"]));

如果这是给你问题的那一行。

If that is the line that is giving you the problem.

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