設置的是第一個字符的顏色，這時richtextBox的rtf中記錄下位置0的顏色，重置text時，在rtf中的位置從位置0開始,因此顏色還是Color.Red,第三次也應該同樣如此
richTextBox1.Text = "123";
richTextBox1.Select(0, 1);
richTextBox1.SelectionColor = Color.Red;
richTextBox1.Clear();//清除文本，包括樣式
//或richTextBox1.Text="";
richTextBox1.Text = "abc";
richTextBox1.Text = "efg";
這樣重置後的文本顏色就會是黑色.
【關鍵字著色】
public partial class RichTextBox : Form
...{
public RichTextBox()
...{
InitializeComponent();
}
private void tSql_TextChanged(object sender, EventArgs e) //文本框改變事件
...{
int index = this.tSql.SelectionStart; //記錄修改的位置
this.tSql.SelectAll();
this.tSql.SelectionColor = Color.Black;
string[] keystr =...{ "select ", "from ", "where ", " and ", " or ", " order ", " by ", " desc ", " when ", " case ",
" then ", " end ", " on ", " in ", " is ", " else ", " left ", " join ", " not ", " null " };
for (int i = 0; i < keystr.Length; i++)
this.getbunch(keystr[i], this.tSql.Text);
this.tSql.Select(index, 0); //返回修改的位置
this.tSql.SelectionColor = Color.Black;
}
public int getbunch(string p, string s) //給關鍵字上色
...{
int cnt = 0; int M = p.Length; int N = s.Length;
char[] ss = s.ToCharArray(), pp = p.ToCharArray();
if (M > N) return 0;
for (int i = 0; i < N - M + 1; i++)
...{
int j;
for (j = 0; j < M; j++)
...{
if (ss[i + j] != pp[j]) break;
}
if (j == p.Length)
...{
this.tSql.Select(i, p.Length);
this.tSql.SelectionColor = Color.Blue;
cnt++;
}
}
return cnt;
}
}
【繪制顏色提議】
最好的做法是繼承RichTextBox，重載新類的Paint方法。
並且在設置SelectionLength的時候，禁止控件的重繪過程，這樣才不會出現被語法高亮的文本有一個突然選中的過程。
以下2個方法將會對你解決這一問題有很大的幫助.
[DllImport("user32")]
private static extern int SendMessage(IntPtr hwnd, int wMsg, int wParam, IntPtr lParam);
private const int WM_SETREDRAW = 0xB;
//停止控件的重繪
private void BeginPaint()
{
SendMessage(yourRichTextBox.Handle, WM_SETREDRAW, 0, IntPtr.Zero);
}
//允許控件重繪.
private void EndPaint()
{
SendMessage(yourRichTextBox.Handle, WM_SETREDRAW, 1, IntPtr.Zero);
yourRichTextBox.Refresh();
}
