c#-用于自定义控件的文本框字符串/文本填充

我是新手,最近我问了这个question,它告诉我在TextBox的底部边框上有我的最佳选择,它可以防止由于绘制图形而导致的闪烁/撕裂.

现在我的问题是如何在文本框中包含文本/字符串的边距/填充,这是代码：

using System.Drawing;
using System.Windows.Forms;

namespace main.Classes.CustomControls {

    class TextBoxMaterial : TextBox {
        public TextBoxMaterial() {
            this.BorderStyle = System.Windows.Forms.BorderStyle.None;
            this.Controls.Add(new Label() {
                Height = 2,
                Dock = DockStyle.Bottom,
                BackColor = Color.Gray,
            });
        }
    }
}

当前文本框：

我需要具备的条件：

解决方法:

您可以通过发送EM_SETMARGINS来设置TextBox文本的左填充和右填充.还可以将TextBox的AutoSize属性设置为false,以能够更改控件的高度.
结果如下：

using System;
using System.Runtime.InteropServices;
using System.Windows.Forms;
using System.Drawing;
public class ExTextBox : TextBox
{
    [DllImport("user32.dll")]
    private static extern IntPtr SendMessage(IntPtr hwnd, int msg,
        int wParam, int lParam);
    private const int EM_SETMARGINS = 0xd3;
    private const int EC_RIGHTMARGIN = 2;
    private const int EC_LEFTMARGIN = 1;
    private int p = 10;
    public ExTextBox()
        : base()
    {
        var b = new Label { Dock = DockStyle.Bottom, Height = 2, BackColor = Color.Gray };
        var l = new Label { Dock = DockStyle.Left, Width = p, BackColor = Color.White };
        var r = new Label { Dock = DockStyle.Right, Width = p, BackColor = Color.White };
        AutoSize = false;
        Padding = new Padding(0);
        BorderStyle = System.Windows.Forms.BorderStyle.None;
        Controls.AddRange(new Control[] { l, r, b });
    }
    protected override void OnHandleCreated(EventArgs e)
    {
        base.OnHandleCreated(e);
        SetMargin();
    }
    private void SetMargin()
    {
        SendMessage(Handle, EM_SETMARGINS, EC_RIGHTMARGIN, p << 16);
        SendMessage(Handle, EM_SETMARGINS, EC_LEFTMARGIN, p);
    }
}

若要知道右标签的作用,请尝试不将其添加到控件中,然后将长文本写入TextBox并通过箭头键转到文本的结尾,然后再使用箭头键回到开头.

标签：margins,padding,c,user-interface,winforms
来源： https://codeday.me/bug/20191118/2027865.html