zoukankan      html  css  js  c++  java
  • cannot implicitly convert type 'bool?' to 'bool'. An explicit conversion exists (are you missing a cast?)

    cannot implicitly convert type 'bool?' to 'bool'. An explicit conversion exists (are you missing a cast?)

    As the others stated bool? is not equal to bool. bool? can also be null, see Nullable<t> (msdn).

    If you know what the null state wants to imply, you easily can use the ?? - null-coalescing operator (msdn) to convert your bool? to bool without any side effects (Exception).

    Example:

    //Let´s say "chkDisplay.IsChecked = null" has the same meaning as "chkDisplay.IsChecked = false" for you
    //Let "check" be the value of "chkDisplay.IsChecked", unless "chkDisplay.IsChecked" is null, in which case "check = false"
    
    bool check = chkDisplay.IsChecked ?? false;

    举例

       var systemWeb = Element.Element("system.web");
                var compilation = systemWeb?.Element("compilation");
                var assemblies = compilation?.Element("assemblies");
                if (assemblies != null)
                {
                    foreach (var li in RemoveList)
                    {
                        IEnumerable<XElement> targetElements = assemblies.Elements("add").Where(s => s.Attribute("assembly").Value.Contains(li));
                        targetElements.Remove();
                    }
                }

    需要修改为

     var systemWeb = Element.Element("system.web");
                var compilation = systemWeb?.Element("compilation");
                var assemblies = compilation?.Element("assemblies");
                if (assemblies != null)
                {
                    foreach (var li in RemoveList)
                    {
                        IEnumerable<XElement> targetElements = assemblies.Elements("add")
                            .Where(s => s.Attribute("assembly")?.Value.Contains(li) ?? false);
                        targetElements.Remove();
                    }
                }
  • 相关阅读:
    晨考总结第二天
    晨考总结第一天
    常用的设计模式总结
    AOP底层原理剖析
    Spring AOP
    jstat统计输出说明
    zabbix 触发器匹配字符串告警
    hive部分常用函数
    nginx日志说明
    windwos文件句柄数限制
  • 原文地址:https://www.cnblogs.com/chucklu/p/12849486.html
Copyright © 2011-2022 走看看