限制WPF textbox 字符最大值

最新推荐文章于 2023-03-28 17:22:13 发布

转载最新推荐文章于 2023-03-28 17:22:13 发布 · 1.2k 阅读

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原文链接：http://www.cnblogs.com/canyuexingchen/p/8110320.html

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本文介绍了一个WPF行为，用于根据绑定属性上的StringLength特性自动设置TextBox的最大长度。此行为通过反射获取绑定属性上的StringLength特性，并相应地设置TextBox的最大长度。

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/// <summary>
/// Set the maximum length of a TextBox based on any StringLength attribute of the bound property
/// </summary>
public class RestrictStringInputBehavior : Behavior<TextBox>
{
    protected override void OnAttached()
    {
        AssociatedObject.Loaded += (sender, args) => setMaxLength();
        base.OnAttached();
    }

    private void setMaxLength()
    {
        object context = AssociatedObject.DataContext;
        BindingExpression binding = AssociatedObject.GetBindingExpression(TextBox.TextProperty);

        if (context != null && binding != null)
        {
            PropertyInfo prop = context.GetType().GetProperty(binding.ParentBinding.Path.Path);
            if (prop != null)
            {
                var att = prop.GetCustomAttributes(typeof(StringLengthAttribute), true).FirstOrDefault() as StringLengthAttribute;
                if (att != null)
                {
                    AssociatedObject.MaxLength = att.MaximumLength;
                }
            }
        }
    }
}
You can see, the behavior simply retrieves the data context of the text box, and its binding expression for "Text". Then it uses reflection to get the "StringLength" attribute. Usage is like this:
<UserControl
    xmlns:i="clr-namespace:System.Windows.Interactivity;assembly=System.Windows.Interactivity"

    <TextBox Text="{Binding SomeProperty}">
        <i:Interaction.Behaviors>
            <local:RestrictStringInputBehavior />
        </i:Interaction.Behaviors>
    </TextBox>

</UserControl>

<UserControl
    xmlns:i="clr-namespace:System.Windows.Interactivity;assembly=System.Windows.Interactivity"

    <TextBox Text="{Binding SomeProperty}">
        <i:Interaction.Behaviors>
            <local:RestrictStringInputBehavior />
        </i:Interaction.Behaviors>
    </TextBox>

</UserControl>

转载于:https://www.cnblogs.com/canyuexingchen/p/8110320.html