构造数组时出现问题(在SQL语句之后) [英] Problem constructing an Array (after SQL statement)

问题描述

我说实话:这是一个荒谬的问题，我花了一个多小时，因为那四行代码，但是我想不清楚，不知道是否是因为它的5550 am ...

I''ll me honest: its a ridiculous problem, I''ve spent more than hour because those 4 lines of code, but I cant think clearly, dont know if its because its 5550 am...

cmd = new SqlCommand("Select Texto FROM Notes WHERE ID_users='" + id_user.ToString() + "'", conn);
          SqlDataReader dr = cmd.ExecuteReader();
          int num = 9; // static variable to change later
          string[] texto = new string[num];
         
               while (dr.Read())
               {
                   for (int i = 0; i < num; i++)
                   {
                       texto[i] = dr[0].ToString();
                   }
               }

所以问题是，该SQL语句的结果是其简单的9个不同的字符串.我想将它们存储在Array-texto中.

但是由于某些(显而易见的)原因，数组中的所有字段都相同(SQL查询的最后结果).

So the problem is, the result from that SQL statement its simple 9 different strings. And I want to store them in Array - texto.

But for some (obvious) reason, all fields from array gets the same (the last result from sql query).

Can you please help me?

推荐答案

Maxxdd，

您正在使用嵌套循环，这就是问题所在.从此处删除for循环，并在while循环之前声明i，然后在赋值之后递增i.

Hi Maxxdd,

You are using nested loop here that is the problem. Remove for loop from there and declare i before while loop and increment i after assignment.

int i;
i=0;                     
                while (dr.Read())
                {
                  texto[i] = Convert.ToString(dr[0]);
                  i++;
                }

使用convert.ToString因为如果dr [0]中的字符串为null，它将不会通过异常，否则会导致null指针异常

Used convert.ToString Beacuse if the string in dr[0] in null it will not through an exception otherwise it througs null pointer exception

for (int i = 0; i <= dr.RecordsAffected - 1; i++) {
    texto[i] = dr(0);
}

我想添加的一件事是使用sql参数来防止sql注入:

例如:

one more thing i would like to add is to use sql parameters to prevent sql injections :

for example:

cmd = new SqlCommand("Select Texto FROM Notes WHERE ID_users=@Iduser, conn);

SqlParameter param = new SqlParameter();
param.ParameterName = "@Iduser";
param.Value = id_user.ToString();
param.Size = 15;
param.SqlDbType = System.Data.SqlDbType.VarChar;

cmd.Parameters.Add(param);

干杯！

Cheers!

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