无法确定条件表达式的类型，因为有'廉政'之间的隐式转换'<&空GT;' [英] Type of conditional expression cannot be determined because there is no implicit conversion between 'int' and '<null>'

问题描述

这是我的代码：

int? BankName_dd = 
int.Parse((e.Item.FindControl("BankName_dd") as DropDownList).SelectedValue) != -1 ? 
int.Parse((e.Item.FindControl("BankName_dd") as DropDownList).SelectedValue) : null;

但我不明白为什么这个错误被提出任何建议？

but I don't understand why this error is being raised any suggestions ?

推荐答案

这是因为编译器试图先评估右侧。

it happens because compiler tries to evaluate the right hand side first.

int.Parse（（e.Item.FindControl（BankName_dd）as DropDownList）.SelectedValue）是int且不可为空，因此参数之间不匹配ie int和null

int.Parse((e.Item.FindControl("BankName_dd") as DropDownList).SelectedValue) is int and not nullable so there is a mismatch between parameters i.e int and null

即使这样做也不错。现在将第一个参数清除为null int

Even this would be fine if you do it. this now wakes the first parameter as nullable int

int? BankName_dd = int.Parse((e.Item.FindControl("BankName_dd") as DropDownList).SelectedValue) != -1 ? (int?)int.Parse((e.Item.FindControl("BankName_dd") as DropDownList).SelectedValue):null;

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