手动更改kendo ui工具栏切换按钮不起作用(manually change kendo ui toolbar toggle button not working)

 该错误不是由Random.Next引起的，因为即使Next由于循环条件i < numberOfNumerics返回4，也只循环3个数字。 所以这是正确的。 
 
 错误是由错误的逻辑引起的。 你用： 
 
builder.Replace(builder[replaceIndex],d);
 
 用您的数字代替所有出现的字母。 你想要使用： 
 
builder[replaceIndex] = d;
 
 但是你应该存储已经被替换的索引，否则你可以替换它们： 
 
var replacedIndexes = new HashSet<int>();
for (int i = 0; i < numberOfNumerics; i++)
{
    int replaceIndex = random.Next(0, builder.Length);
    while (!replacedIndexes.Add(replaceIndex))
        replaceIndex = random.Next(0, builder.Length);
    char d = digits[random.Next(0, digits.Length)];
    builder[replaceIndex] = d;
}

The error is not caused by Random.Next since you loop only 3 numbers even if Next can return 4 because of your loop condition i < numberOfNumerics. So this is correct. 
 
The error is caused by a wrong logic. You use:
 
builder.Replace(builder[replaceIndex],d);
 
That replaces all occurrences of a letter with your digit. You want to use:
 
builder[replaceIndex] = d;
 
But you should store the already replaced indexes otherwise you could replace the same:
 
var replacedIndexes = new HashSet<int>();
for (int i = 0; i < numberOfNumerics; i++)
{
    int replaceIndex = random.Next(0, builder.Length);
    while (!replacedIndexes.Add(replaceIndex))
        replaceIndex = random.Next(0, builder.Length);
    char d = digits[random.Next(0, digits.Length)];
    builder[replaceIndex] = d;
}