[英]How can i assign a value to a char variable in a foreach loop? C#
I am trying to do is something like this:我想做的是这样的:
StringBuilder sb = new StringBuilder();
foreach(char ch in valor)
{
if (ch == ',')
ch = '.';
else if (ch == '0' || ch == '1' || ch == '2' || ch == '3' || ch == '4' || ch == '5' || ch == '6' || ch == '7' || ch == '8' || ch == '9' || ch == ',')
{
sb.Append(ch);
}
}
What I want is, if the character is a comma, to make it a dot.我想要的是,如果字符是逗号,则将其设为点。 But i get the following error
但我收到以下错误
it is not possible to assign value to 'ch' because it is a foreach interaction variable
无法为“ch”赋值,因为它是一个 foreach 交互变量
Why not append in both if branches?为什么不在两个 if 分支中使用 append?
foreach(char ch in valor)
{
if (ch == ',')
{
sb.Append('.');
}
else if (ch == '0' || ch == '1' || ch == '2' || ch == '3' || ch == '4' || ch == '5' || ch == '6' || ch == '7' || ch == '8' || ch == '9')
{
sb.Append(ch);
}
}
Just introduce a local variable只需引入一个局部变量
StringBuilder sb = new StringBuilder();
foreach(char ch in valor)
{
var tmp = ch == ',' ? '.' : ch;
if (char.IsDigit(tmp) || tmp == '.')
{
sb.Append(tmp);
}
}
You can also use the static char.IsDigit()
method to check whether a char is a digit or not您还可以使用 static
char.IsDigit()
方法来检查 char 是否为数字
You could also do it only with linq:你也可以只用 linq 来做:
var sb = new StringBuilder();
sb = valor
.Select(c => c == ',' ? '.' : c)
.Where(c => char.IsDigit(c) || c == '.')
.Aggregate(sb, (sb, c) => sb.Append(c));
Short answer : it is impossible .简短的回答:这是不可能的。
Using an immutable foreach
indexed item you need to use an intermediate variable like that:使用不可变的
foreach
索引项,您需要使用这样的中间变量:
foreach ( char ch in valor )
{
char c = ch;
if ( c == ',' )
{
c = '.';
}
if ( c == '0' || c == '1' || c == '2' || c == '3' || c == '4'
|| c == '5' || c == '6' || c == '7' || c == '8' || c == '9'
|| c == '.' )
{
sb.Append(c);
}
}
I removed the else
because it seems to be a mistake...我删除了
else
,因为它似乎是一个错误......
But in this case you may prefer directly use a for
to avoid this useless intermediate variable and so to optimize speed and memory:但在这种情况下,您可能更喜欢直接使用
for
来避免这个无用的中间变量,从而优化速度和 memory:
for (int index = 0; index < valor.Length; index++)
{
char c = valor[index];
if ( c == ',' )
{
c = '.';
}
if ( c == '0' || c == '1' || c == '2' || c == '3' || c == '4'
|| c == '5' || c == '6' || c == '7' || c == '8' || c == '9'
|| c == '.' )
{
sb.Append(c);
}
}
Next, in the case of the code provided, we can refactor like that, using the else
in the right way now:接下来,对于提供的代码,我们可以像这样重构,现在以正确的方式使用
else
:
for (int index = 0; index < valor.Length; index++)
{
char c = valor[index];
if ( c == ',' )
{
sb.Append('.');
}
else
if ( c == '0' || c == '1' || c == '2' || c == '3' || c == '4'
|| c == '5' || c == '6' || c == '7' || c == '8' || c == '9' )
{
sb.Append(c);
}
}
Also, in the case of the code provided, we can improve to this:此外,在提供代码的情况下,我们可以对此进行改进:
for ( int index = 0; index < valor.Length; index++ )
{
char c = valor[index];
if ( c == ',' )
{
sb.Append('.');
}
else
if ( char.IsDigit(c) ) // or IsNumber
{
sb.Append(c);
}
}
And to optimize better:为了更好地优化:
for ( int index = 0; index < valor.Length; index++ )
{
char c = valor[index];
if ( c == ',' )
{
sb.Append('.');
}
else
if ( c >= '0' && c <= '9' )
{
sb.Append(c);
}
}
So using a foreach
we can write, but a little less optimized while being more clean:因此,我们可以使用
foreach
编写,但优化程度较低,但更干净:
foreach (char ch in valor )
{
if ( ch == ',' )
{
sb.Append('.');
}
else
if ( ch >= '0' && ch <= '9' )
{
sb.Append(ch);
}
}
Char.IsDigit Method Char.IsDigit 方法
Char.IsNumber Method Char.IsNumber 方法
You can try this:你可以试试这个:
StringBuilder sb = new StringBuilder();
var valor = "google,com1234";
if (valor.Contains(','))
{
valor = valor.Replace(",", ".");
}
foreach (char ch in valor)
{
if (ch == '0' || ch == '1' || ch == '2' || ch == '3' || ch == '4' || ch == '5' || ch == '6' || ch == '7' || ch == '8' || ch == '9' || ch == '.')
{
sb.Append(ch);
}
}
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