為什么我的richtextbox 不改變顏色？

Question

我試圖在我的子網計算器中為我的richtextbox 中的字母提供不同的 colors，但是richtextbox 直到第 26 個字母才改變 colors。

它的外觀：

        int iValueSm = trackBarSmMask.Value;
        rtbScroll.Text = "";
        rtbScroll.SelectionStart = rtbScroll.TextLength;
        rtbScroll.SelectionLength = 0;

        for (int i = 1; i <= iValueSm; i++)
        {
            rtbScroll.SelectionColor = Color.Blue;
            rtbScroll.AppendText("N");              

            if (i%8==0 && i != 32)
            {
                rtbScroll.Text = rtbScroll.Text + "."; 
            }
        }

        for (int i = iValueSm+1; i <= 32; i++)
        {
            rtbScroll.SelectionColor = Color.Red;
            rtbScroll.AppendText("H");              

            if (i % 8 == 0 && i != 32)
            {
                rtbScroll.Text = rtbScroll.Text + ".";
            }
        }

        labelAmountNetID.Text = "/" + iValueSm.ToString();

Answer 1

任何時候設置 .Text() 屬性，都會將所有格式重置為黑白。

這是我使用 SelectedText 編寫它的方式：

private void Form1_Load(object sender, EventArgs e)
{
    updateRTB();
}

private void trackBarSmMask_ValueChanged(object sender, EventArgs e)
{
    updateRTB();
}

private void trackBarSmMask_Scroll(object sender, EventArgs e)
{
    updateRTB();
}

private void updateRTB()
{            
    rtbScroll.Text = "";
    rtbScroll.SelectionStart = 0;
    rtbScroll.SelectionLength = 0;
    int iValueSm = trackBarSmMask.Value;
    labelAmountNetID.Text = "/" + iValueSm.ToString();
    for (int i = 1; i <= 32; i++)
    {
        rtbScroll.SelectionColor = (i <= iValueSm) ? Color.Blue : Color.Red;
        rtbScroll.SelectedText = (i <= iValueSm) ? "N" : "H";
        if (i % 8 == 0 && i != 32)
        {
            rtbScroll.SelectionColor = Color.Black;
            rtbScroll.SelectedText = ".";
        }
    }
}

Answer 2

好吧，可以有很多方法來處理這個問題，但這里有一個建議：

// Track bar definitions...
 private void SetTrackBarVals()
 {
     trackBar1.Minimum = 0;
     trackBar1.Maximum = 31;
 }

 private void trackBar1_Scroll(object sender, EventArgs e)
 {
     var counter = 0;
     var dotsCounter = 0;
     rtbScroll.Text = "";
     int iValueSm = trackBar1.Value + 1; // +1 because we start counting from 0

     for (int i = 1; i <= 32; i++)
     {
         if (counter > 0 && counter % 8 == 0)
         {
             // new octet
             rtbScroll.AppendText(".");
             dotsCounter++;
         }

         if (i > iValueSm)
         {
             // It is red
             rtbScroll.AppendText("H");
             rtbScroll.SelectionStart = (i - 1) + dotsCounter;
             rtbScroll.SelectionLength = 1 ;
             rtbScroll.SelectionColor = Color.Red;
         }
         else
         {
             rtbScroll.AppendText("N");
         }

         counter++;
     } 
 }