c# - 将一组文本框控件更改为 ReadOnly = false

Question

我有一组文本框控件，我想将其更改为只读。我的代码片段如下。 ReadOnly 行给出错误“控件没有 ReadOnly 的定义...”我相信这个问题与 TextBoxBase 类中的 ReadOnly 功能有关。我怎样才能解决这个问题并访问 TextBoxBase 类？

        foreach (Control c in fraPParameters.Controls)
        {
            if (c is Label)
            {
                c.Visible = false;
                c.Text = string.Empty;
                c.Tag = string.Empty;
                tt.SetToolTip(c, null);
            }

            if (c is TextBox)
            {
                c.Visible = false;
                c.ReadOnly = false;
                c.Text = string.Empty;
                c.Tag = string.Empty;
                tt.SetToolTip(c, null);
                c.BackColor = Color.White;
            }
        }

Answer 1

使用 Type Pattern它测试表达式是否可以转换为指定类型，如果可以，则将其转换为该类型的变量。

When using the type pattern to perform pattern matching, is tests whether an expression can be converted to a specified type and, if it can be, casts it to a variable of that type. It is a straightforward extension of the is statement that enables concise type evaluation and conversion. The general form of the is type pattern is:

expr is type varname

示例

if (sender is TextBox textBox) 
{
    textBox.Visible = false;
    textBox.ReadOnly = false;
    textBox.Text = string.Empty;
    textBox.Tag = string.Empty;
    ...

此外，您可能只想使用带有模式匹配的 switch 语句，如 Callum Watkins 所述在评论中

foreach (Control c in fraPParameters.Controls)
{
    switch (c)
    {
        case TextBox textbox:
            textbox.Visible = false;
            textbox.ReadOnly = false;
            textbox.Text = string.Empty;
            textbox.Tag = string.Empty;
            //...
            break;
        case Label label:
            label.Visible = false;
            label.Text = string.Empty;
            label.Tag = string.Empty;
            //...
            break;

    }
}

---

其他资源

is (C# Reference)

Checks if an object is compatible with a given type, or (starting with C# 7.0) tests an expression against a pattern.

Using pattern matching switch statements