C# Nullable<DateTime> 到字符串
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C# Nullable<DateTime> to string
提问by JL.
I have a DateTime?variable, sometimes the value is null, how can I return an empty string ""when the value is nullor the DateTimevalue when not null?
我有一个DateTime?变量，有时值null，我怎么能返回一个空字符串""当值null或DateTime值时不null？
采纳答案by Jon Seigel
string date = myVariable.HasValue ? myVariable.Value.ToString() : string.Empty;回答by Ahmed Khalaf
DateTime? MyNullableDT;
....
if (MyNullableDT.HasValue)
{
return MyNullableDT.Value.ToString();
}
return "";
回答by Cecil Has a Name
DateTime? d;
// stuff manipulating d;
return d != null ? d.Value.ToString() : String.Empty;
回答by Mike
if (aDate.HasValue)
return aDate;
else
return string.Empty;
回答by Patrick Desjardins
DateTime d?;
string s = d.HasValue ? d.ToString() : string.Empty;
回答by JaredPar
You could write an extension method
你可以写一个扩展方法
public static string ToStringSafe(this DateTime? t) {
return t.HasValue ? t.Value.ToString() : String.Empty;
}
...
var str = myVariable.ToStringSafe();
回答by Joey
Actually, this is the default behaviour for Nullable types, that without a value they return nothing:
实际上，这是 Nullable 类型的默认行为，如果没有值，它们将不返回任何内容：
public class Test {
public static void Main() {
System.DateTime? dt = null;
System.Console.WriteLine("<{0}>", dt.ToString());
dt = System.DateTime.Now;
System.Console.WriteLine("<{0}>", dt.ToString());
}
}
this yields
这产生
<>
<2009-09-18 19:16:09>
回答by Eric Lippert
Though many of these answers are correct, all of them are needlessly complex. The result of calling ToString on a nullable DateTime is already an empty string if the value is logically null.Just call ToString on your value; it will do exactly what you want.
尽管这些答案中有许多是正确的，但它们都不必要地复杂。如果值在逻辑上为空，则在可为空的 DateTime 上调用 ToString 的结果已经是空字符串。只需在您的值上调用 ToString ；它会做你想要的。
回答by DJ.
Calling .ToString()on a Nullable<T>that is nullwill return an empty string.
调用.ToString()a Nullable<T>that isnull将返回一个空字符串。
回答by Jalal
All you need to do is to just simply call .ToString(). It handles Nullable<T>object for nullvalue.
您需要做的只是简单地调用.ToString(). 它处理Nullable<T>对象的null价值。
Here is the source of .NET Frameworkfor Nullable<T>.ToString():
这里是.NET框架的来源为Nullable<T>.ToString()：
public override string ToString() {
return hasValue ? value.ToString() : "";
}
