问个简单的问题，关于richtextbox中find方法的reverse

Question

索引值是跟顺序查找时一样，从文本开头开始的么？
怎么每次查找都是只能找到文本最后那个符合的字符串？
谢谢啦。

Answer 1

使用public int Find(string str, int start, int end, RichTextBoxFinds options)

Answer 2

但是只找到了第一个出现位置，更改star的位置结果还是一样。   

Answer 3

private void button1_Click(object sender, EventArgs e)
        {
           
            this.richTextBox1.SelectionColor = this.richTextBox1.ForeColor;
            string str = "b";
            if (lastIndex == -1)
            {
                lastIndex = this.richTextBox1.Text.Length - 1;
            }
            lastIndex = this.richTextBox1.Find(str, 0, lastIndex, RichTextBoxFinds.Reverse);
            if (lastIndex != -1)
            {
                this.richTextBox1.SelectionStart = lastIndex;
                this.richTextBox1.SelectionLength = str.Length;
            }
            this.richTextBox1.SelectionColor = Color.Red;
        }

Answer 4

private void button1_Click(object sender, EventArgs e)
        {
           
            this.richTextBox1.SelectionColor = this.richTextBox1.ForeColor;
            string str = "b";
            if (lastIndex + 1 == this.richTextBox1.Text.Length)
            {
                lastIndex = -1;
            }
            lastIndex = this.richTextBox1.Find(str, lastIndex + 1, this.richTextBox1.Text.Length - 1, RichTextBoxFinds.None);
            if (lastIndex != -1)
            {
                this.richTextBox1.SelectionStart = lastIndex;
                this.richTextBox1.SelectionLength = str.Length;
            }
            this.richTextBox1.SelectionColor = Color.Red;
        }
下次要记得放分