字符串之间的区别是什么。空和“”，是他们 可以互换

字符串。Empty是一个只读字段，而""是一个编译时常量。他们表现不同的地方有:

c# 4.0或更高版本中的默认参数值

void SomeMethod(int ID, string value = string.Empty)
// Error: Default parameter value for 'value' must be a compile-time constant
{
    //... implementation
}

switch语句中的大小写表达式

string str = "";
switch(str)
{
    case string.Empty: // Error: A constant value is expected. 
        break;

    case "":
        break;

}

属性参数

[Example(String.Empty)]
// Error: An attribute argument must be a constant expression, typeof expression 
//        or array creation expression of an attribute parameter type

字符串。Empty是只读字段，而""是const字段。这意味着您不能使用String。在switch语句中为空，因为它不是常量。

字符串之间的区别是什么。空和“”，是他们 可以互换

字符串。Empty是一个只读字段，而""是一个编译时常量。他们表现不同的地方有:

c# 4.0或更高版本中的默认参数值

void SomeMethod(int ID, string value = string.Empty)
// Error: Default parameter value for 'value' must be a compile-time constant
{
    //... implementation
}

switch语句中的大小写表达式

string str = "";
switch(str)
{
    case string.Empty: // Error: A constant value is expected. 
        break;

    case "":
        break;

}

属性参数

[Example(String.Empty)]
// Error: An attribute argument must be a constant expression, typeof expression 
//        or array creation expression of an attribute parameter type

另一个区别是字符串。Empty生成更大的CIL代码。而用于引用“”和String的代码。Empty是相同的长度，编译器不会为string优化字符串连接(参见Eric Lippert的博客文章)。空的参数。以下等价函数

string foo()
{
    return "foo" + "";
}
string bar()
{
    return "bar" + string.Empty;
}

生成这个IL

.method private hidebysig instance string foo() cil managed
{
    .maxstack 8
    L_0000: ldstr "foo"
    L_0005: ret 
}
.method private hidebysig instance string bar() cil managed
{
    .maxstack 8
    L_0000: ldstr "bar"
    L_0005: ldsfld string [mscorlib]System.String::Empty
    L_000a: call string [mscorlib]System.String::Concat(string, string)
    L_000f: ret 
}

使用字符串。空而不是""。

This is more for speed than memory usage but it is a useful tip. The "" is a literal so will act as a literal: on the first use it is created and for the following uses its reference is returned. Only one instance of "" will be stored in memory no matter how many times we use it! I don't see any memory penalties here. The problem is that each time the "" is used, a comparing loop is executed to check if the "" is already in the intern pool. On the other side, String.Empty is a reference to a "" stored in the .NET Framework memory zone. String.Empty is pointing to same memory address for VB.NET and C# applications. So why search for a reference each time you need "" when you have that reference in String.Empty?

参考:字符串。Empty和""

当您在视觉上扫描代码时，""会像字符串一样呈现彩色。字符串。Empty看起来像常规的类成员访问。在快速浏览的过程中，更容易发现“”或凭直觉理解其含义。

找出字符串(堆栈溢出着色不是很有帮助，但在VS中这是更明显的):

var i = 30;
var f = Math.Pi;
var s = "";
var d = 22.2m;
var t = "I am some text";
var e = string.Empty;