比较datareader返回的值 [英] Compare values returned by datareader

问题描述

以下代码无法评估返回值：

输出默认标签名称。

 SqlDataReader dr = cmd.ExecuteReader（）; 
 
  while （dr.Read（））
 {
 .. 
 sex = dr [< span class =code-string>  sex]。ToString（）; 
 .. 
} 
  if （性别==  < span class =code-string>男性）
 {
 Label1.Text =  标记; 
} 
 其他 如果（性别==  女性）
 {
 Label1.Text =   Marry; 
} 

怎么做？

解决方案

请记住，这只会与您的查询返回的数据库中的最后一个匹配行进行比较：我们不知道您的查询是什么。

因此，如果您有十几行男性然后一行带有Yes please，那么比较只会将Yes please与Male和Female进行比较，并且两者都失败。因此，您的标签的当前内容将不会更改。



因此，为您知道存在问题的按键添加启动器的默认值：

  if （性别==  男性）
 {
 Label1.Text =  标记; 
} 
 其他 如果（性别==  女性）
 {
 Label1.Text =   Marry; 
} 
  else  
 {
 Label1.Text =  未知 +性别; 
} 

从那里你应该有一个更好的主意 - 但检查你的查询只返回一行...还记得字符串比较是大小写敏感...

The following code doesn't working to evaluate the returned value:
Outputs the default Label Name.

SqlDataReader dr = cmd.ExecuteReader();
                
while (dr.Read())
{
..
sex = dr["sex"].ToString();
..
}
if (sex == "Male")
{
   Label1.Text = "Mark";
}
else if(sex == "Female")
{
   Label1.Text = "Marry";
}

How to do this?

解决方案

Remember that this will be comparing only against the last matching row in the database that your query returns: and we don't know what your query is.
So if you have a dozen rows with "Male" and then one row with "Yes please" then the comparison will only compare "Yes please" against "Male" and "Female" and fail both. As a result, the current content of your label will not be changed.

So add a default for starters that keys you know that there is a problem:

if (sex == "Male")
{
   Label1.Text = "Mark";
}
else if(sex == "Female")
{
   Label1.Text = "Marry";
}
else
{
   Label1.Text = "Unknown " + sex;
}

And from there you should get a better idea - but check your query returns only one row as well... Also remember that string comparisons are case sensitive...

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