随机字符生成错误C#

Question

出于某种原因,当我尝试一次性生成此代码时,代码会反复生成相同的数字或字母(30次) - 请参阅下文.但是,当我在调试模式下逐行浏览时,代码效果很好......

private string Generate_ActiveX_name()
{

    StringBuilder charBuilder = new StringBuilder("abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ");
    StringBuilder numBuilder = new StringBuilder("0123456789");
    // 
    // Holds Active X Key (final)
    //
    StringBuilder activeX_builder = new StringBuilder();

    // Determine charactar or number


    while (activeX_builder.Length < 30)
    {

        Random activeX_gen = new Random();

        switch (activeX_gen.Next(0, 2))
        {
            case 0:
                Random charSelection = new Random();
                int CharSelected = charSelection.Next(0, 53);
                activeX_builder.Append(charBuilder[CharSelected]);
                break;
            case 1:
                Random numSelection = new Random();
                int NumSelected = numSelection.Next(0, 10);
                activeX_builder.Append(numBuilder[NumSelected]);
                break;

        }
    }

    string activeX_key = activeX_builder.ToString().Substring(0, 8) + "-";
    activeX_key += activeX_builder.ToString().Substring(8, 4) + "-";
    activeX_key += activeX_builder.ToString().Substring(12, 4) + "-";
    activeX_key += activeX_builder.ToString().Substring(16, 11);

    return activeX_key;

}

为什么这个代码在我一次运行时会失败？

谢谢,埃文

Answer 1

您需要将Random构造函数移出循环.改变这个:

while (activeX_builder.Length < 30)
{
    Random activeX_gen = new Random();

至:

Random activeX_gen = new Random();
while (activeX_builder.Length < 30)
{

问题在于,当Random创建实例时,它使用当前系统时钟作为随机数生成的"种子"值.由于您的例程运行速度非常快,因此每次都会选择相同的种子,因此您将获得相同的"随机"值.当你进行调试时,你会减慢它(通过步进)的速度,以便在每个循环中选择不同的种子,并获得真正的随机值.

如果将其移出循环,则将Random创建单个实例,这将导致随机分布(并且效率更高!).