winfrom textbox文本垂直居中

要实现Winform中TextBox文本垂直居中，可以通过代码来设置。首先，可以在TextBox的属性中设置Multiline为True，这样就可以在TextBox中输入多行文本。接着，可以使用以下代码来实现文本垂直居中：

private void Form1_Load(object sender, EventArgs e)
{
    textBox1.Multiline = true;
    textBox1.TextAlign = HorizontalAlignment.Center;
    textBox1.TextChanged += TextBox1_TextChanged;
    TextBox1_TextChanged(null, null);
}

private void TextBox1_TextChanged(object sender, EventArgs e)
{
    int numberOfLines = textBox1.GetLineFromCharIndex(textBox1.TextLength) + 1;
    int lineHeight = textBox1.Height / numberOfLines;
    if (lineHeight > 0)
    {
        SendMessage(textBox1.Handle, EM_SETRECT, IntPtr.Zero, (IntPtr)new RECT { Top = (textBox1.Height - lineHeight) / 2, Bottom = (textBox1.Height + lineHeight) / 2 });
    }
}

[StructLayout(LayoutKind.Sequential)]
private struct RECT
{
    public int Left;
    public int Top;
    public int Right;
    public int Bottom;
}

private const int EM_SETRECT = 0xB3;

[DllImport("user32.dll")]
private static extern IntPtr SendMessage(IntPtr hWnd, int msg, IntPtr wp, IntPtr lp);

这段代码利用了TextBox的GetLineFromCharIndex和EM_SETRECT属性，先计算文本行数和每行的高度，然后通过SendMessage方法设置文本的垂直居中。这样，就可以实现Winform中TextBox文本的垂直居中显示。