c＃中的字符串连接 [英] string concatenation in c#

问题描述

下面是我想用字符串连接字符串变量的代码：

  public  < span class =code-keyword> void  formQueryString（）
 {
  string  filterQuery; 
  int  chk =  0 ; 
  if （rbHomeDelivery.Checked）
 {
 filterQuery =   Home_Delivery like yes; 
 chk =  1 ; 
} 
  if （rbTakeaway.Checked）
 {
 filterQuery =    Take_Away like yes; 
 chk =  1 ; 
} 
 如果（cbOpenAllDay.Checked&& chk ==  1  ）
 {
 filterQuery = filterQuery +  或Open_All_Day like yes;  //  有错误的行 
} 
  else  
 {
 filterQuery = filterQuery +   Open_All_Day like yes< /跨度>; 
} 
} 

给出错误使用未分配的局部变量fi​​lterQuery。



现在我不知道为什么会出错。



请告诉我错误


提前致谢。

解决方案

尝试初始化filterQuery

like string filterQuery = 或字符串filterQuery = string.Empty;

只需在<$ p $的地方添加

 string filterQuery =; 

p> string filterQuery;

尽管每个人都给出了正确答案。我想补充更多。



自己说出错是什么问题。您遇到问题的行是使用filterQuery变量。您可以在声明时指定字符串的默认值，也可以在连接时添加一些条件。但最好的选择是分配默认值，或者你可以在字符串的情况下说空白。



每当你创建一些变量时别忘了给一些值赋值防止这种错误。有时您可能无法测试所有可能的情况。因此，解决此类错误的最佳方法是，

  //  示例 
 字符串 str = 默认（字符串）; 
客户cust = 默认（客户）; 

希望这对你有帮助。



祝你好运

-Amit

Below is the code where I want to concatenate a string variable with string:

public void formQueryString()
        {
            string filterQuery;
            int chk=0;
            if (rbHomeDelivery.Checked)
            {
                filterQuery = "Home_Delivery like yes";
                chk=1;
            }
            if(rbTakeaway.Checked)
            {
                filterQuery = "Take_Away like yes";
                chk=1;
            }
            if (cbOpenAllDay.Checked && chk==1)
            {
                filterQuery = filterQuery + " or Open_All_Day like yes"; //Line with error
            }
            else
            {
                filterQuery = filterQuery + "Open_All_Day like yes";
            }
        }

It is giving error that "use of unassigned local variable filterQuery ".

Now I don't know why it is giving error.

Please let me know the error

Thanks in advance.

解决方案

try to initialize filterQuery
like string filterQuery="" or string filterQuery=string.Empty;

simply add

string filterQuery="";

at the place of

string filterQuery;

Hi,

Although everyone gives the correct answer. i would like to add more.

Error it self says what is the problem. The line where you are having issue is using filterQuery variable. Either you can assign default value of the string at the time of declaration or you need to add some conditions at the time of concatenation. but the best option is to assign default value or you can say blank in case of string.

Whenever you are creating some variable don't forget to assign some value to prevent such kind of errors. Sometimes you may not able to test all the possible scenarios. so best way to solve such error is,

//examples
String str = default(String);
Customer cust = default(Customer);

Hope this will help you.

Best luck
-Amit

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