如何在linq表达式中处理null值 [英] How to handle null value in linq expression

问题描述

我有这个代码

i have this code

var faSummaryForReviewReport = from p in dt.AsEnumerable()
                               where p.Field<string>("Section") == "Reports" && p.Field<string>("Key") == "FASummaryOnReviewReport"
                               select new
                               {
                                   value = p.Field<string>("Value"),
                                   description = p.Field<string>("Description"),
                                   locked = p.Field<bool>("IsLocked")
                               };
       foreach (var user in faSummaryForReviewReport)
       {
           cbFaSummary.SelectedItem.Value = user.value;
           lblFASummary.Text = user.description;
           chkFaSummary.Checked = user.locked;
       }

i在locked = p.Field< bool>中获取空值（IsLocked）



如何处理空值plz帮助我

i am getting null value in " locked = p.Field<bool>("IsLocked")"

how to handle null value plz help me

推荐答案

如果IsLocked可以包含null值然后尝试使用可以为空的布尔值来转换字段的值：

If the IsLocked can contain a null value then try casting the value of the field using a nullable boolean:

...
locked = p.Field<bool?>("IsLocked")
...

你可以在Field方法中使用nullable boolean，但你需要布尔值来设置为Checked属性，这样你就可以检查null和set false（或根据您的要求为真）如下所示

You can use nullable boolean in Field method but you need boolean value to set as Checked property, so you can check for null and set false(or true according to your requirement) as below

locked = p.Field<bool?>("IsLocked")??false

如果哟你使用可以忽略的布尔值如下所示

if you use nullable boolean value as below

locked = p.Field<bool?>("IsLocked")

Set价值如下

Set value as below

chkFaSummary.Checked = user.locked.Value;

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