空文本框是空字符串还是null?

时间:2022-11-13 19:50:02

The text box in question is involved in an if statement within my code, something to the effect of

有问题的文本框涉及我的代码中的if语句,这是有效的

if (textbox.text != "") 
{
    do this
}

I am curious if an empty text box will be considered an empty string or a null statement.

我很好奇,如果一个空文本框将被视为空字符串或空语句。

6 个解决方案

#1


25  

Try to use IsNullOrWhiteSpace, this will make sure of validating the whitespace too without having to trim it.

尝试使用IsNullOrWhiteSpace,这将确保验证空白,而不必修剪它。

if (!string.IsNullOrWhiteSpace(textbox.Text))
{
    //code here
}

According to documentation string.IsNullOrWhiteSpace evaluates to:

根据文档字符串.IsNullOrWhiteSpace评估为:

return String.IsNullOrEmpty(value) || value.Trim().Length == 0;

String.IsNullOrWhiteSpace:

String.IsNullOrWhiteSpace:

Indicates whether a specified string is null, empty, or consists only of white-space characters.

指示指定的字符串是空,空还是仅包含空格字符。

#2


4  

In short it will be an empty string, but you could use the debugger and check that yourself.

简而言之,它将是一个空字符串,但您可以使用调试器并自行检查。

However for best practice use IsNullOrEmpty or IsNullOrWhiteSpace

但是,对于最佳实践,请使用IsNullOrEmpty或IsNullOrWhiteSpace

if (!string.IsNullOrEmpty(textbox.Text)) {

}

Alternatively:

或者:

if (!string.IsNullOrWhiteSpace(textbox.Text)) {

}    

http://msdn.microsoft.com/en-us/library/system.string.isnullorwhitespace.aspx

http://msdn.microsoft.com/en-us/library/system.string.isnullorwhitespace.aspx

#3


3  

It will be an empty string but better to check with this IsNullOrEmpty or IsNullOrWhiteSpace

它将是一个空字符串,但最好检查一下这个IsNullOrEmpty或IsNullOrWhiteSpace

if (!string.IsNullOrEmpty(textbox.text))
{
  //do this
}

IsNullOrWhiteSpace is also take care of whitespace in input string. So if you don't want to execute the code for whitespace too then use second option.

IsNullOrWhiteSpace也会处理输入字符串中的空格。因此,如果您不想执行空格代码,请使用第二个选项。

#4


2  

It will be considered an empty string.

它将被视为空字符串。

#5


-1  

string search = txtSearch.Text.Trim() != "" ? txtSearch.Text.Trim() : "0";

#6


-4  

if (textbox.text != "" || textbox.text != null)

if(textbox.text!=“”|| textbox.text!= null)

#1


25  

Try to use IsNullOrWhiteSpace, this will make sure of validating the whitespace too without having to trim it.

尝试使用IsNullOrWhiteSpace,这将确保验证空白,而不必修剪它。

if (!string.IsNullOrWhiteSpace(textbox.Text))
{
    //code here
}

According to documentation string.IsNullOrWhiteSpace evaluates to:

根据文档字符串.IsNullOrWhiteSpace评估为:

return String.IsNullOrEmpty(value) || value.Trim().Length == 0;

String.IsNullOrWhiteSpace:

String.IsNullOrWhiteSpace:

Indicates whether a specified string is null, empty, or consists only of white-space characters.

指示指定的字符串是空,空还是仅包含空格字符。

#2


4  

In short it will be an empty string, but you could use the debugger and check that yourself.

简而言之,它将是一个空字符串,但您可以使用调试器并自行检查。

However for best practice use IsNullOrEmpty or IsNullOrWhiteSpace

但是,对于最佳实践,请使用IsNullOrEmpty或IsNullOrWhiteSpace

if (!string.IsNullOrEmpty(textbox.Text)) {

}

Alternatively:

或者:

if (!string.IsNullOrWhiteSpace(textbox.Text)) {

}    

http://msdn.microsoft.com/en-us/library/system.string.isnullorwhitespace.aspx

http://msdn.microsoft.com/en-us/library/system.string.isnullorwhitespace.aspx

#3


3  

It will be an empty string but better to check with this IsNullOrEmpty or IsNullOrWhiteSpace

它将是一个空字符串,但最好检查一下这个IsNullOrEmpty或IsNullOrWhiteSpace

if (!string.IsNullOrEmpty(textbox.text))
{
  //do this
}

IsNullOrWhiteSpace is also take care of whitespace in input string. So if you don't want to execute the code for whitespace too then use second option.

IsNullOrWhiteSpace也会处理输入字符串中的空格。因此,如果您不想执行空格代码,请使用第二个选项。

#4


2  

It will be considered an empty string.

它将被视为空字符串。

#5


-1  

string search = txtSearch.Text.Trim() != "" ? txtSearch.Text.Trim() : "0";

#6


-4  

if (textbox.text != "" || textbox.text != null)

if(textbox.text!=“”|| textbox.text!= null)