在不知道属性类型的情况下从属性和列表值获取属性值 [英] Get attribute values from property and list values without knowing the attribute type

问题描述

我想传递属性名称并返回值。这将在通用util中，并且它将不知道属性类型。

I want to pass in the attribute name and return the value. This will be in a generic util and it will not know the attribute type.

更新
如果有人需要这样做，这是实际的工作代码。我需要一种让核心代码在不知道属性的情况下解析属性的方法。

Update This is the actual working code if someone needs to do this. I needed a way to have the core code parse the attributes without knowing what they were.

public void LoadPropertiesToGrid(BaseGridPropertyModel model)
{
    foreach (PropertyInfo prop in ReflectionUtil.FindPublicPropeties(model))
    {
        object editTyp = ReflectionUtil.GetPropertyAttributes(prop, "EditorType"); 
        object rowIdx = ReflectionUtil.GetPropertyAttributes(prop, "ColIndex");
        object name = ReflectionUtil.GetPropertyAttributes(prop, "Name");
        object visible = ReflectionUtil.GetPropertyAttributes(prop, "Visible");
        ConfigureColumn((string) name, (int) rowIdx, (bool) visible, (string) editTyp);
     }
}
[Serializable]
public class CanvasPropertiesViewModel : BaseGridPropertyModel
{
    [PropertiesGrid(Name = "TEsting Name 0", ColIndex = 0)]
    public string StringData1 { get; set; }

    [PropertiesGrid(Name = "TEsting Name 2", ColIndex = 2)]
    public string StringData2 { get; set; }

    [PropertiesGrid(Name = "TEsting Name 1", ColIndex = 1)]
    public string StringData3 { get; set; }
}
[AttributeUsage(AttributeTargets.All, Inherited = false, AllowMultiple = true)]
public sealed class PropertiesGridAttribute : Attribute
{
    /// <summary>
    /// Editor type
    /// </summary>
    public Type EditorType { get; set; }

    /// <summary>
    /// Sets Column Index
    /// </summary>
    public int ColIndex { get; set; }

    /// <summary>
    /// Visible to Grid
    /// </summary>
    public bool Visible { get; set; }

    /// <summary>
    /// Dispaly Name of the property
    /// </summary>
    public string Name { get; set; }
}
public static object GetPropertyAttributes(PropertyInfo prop, string attributeName)
{
    // look for an attribute that takes one constructor argument
    foreach (CustomAttributeData attribData in prop.GetCustomAttributesData())
    {
        string typeName = attribData.Constructor.DeclaringType.Name;
        //if (attribData.ConstructorArguments.Count == 1 && (typeName == attributeName || typeName == attributeName + "Attribute"))
        //{
        //    return attribData.ConstructorArguments[0].Value;
        //}
        foreach (CustomAttributeNamedArgument att in attribData.NamedArguments)
        {
            if(att.GetPropertyValue<string>("MemberName") == attributeName)
            {
                return att.TypedValue.Value;
            }
        }
    }
    return null;
}

//PropertyExpressionParser 
public static TRet GetPropertyValue<TRet>(this object obj, string propertyPathName)
{
    if (obj == null)
    {
        throw new ArgumentNullException("obj");
    }

    string[] parts = propertyPathName.Split('.');
    string path = propertyPathName;
    object root = obj;

    if (parts.Length > 1)
    {
        path = parts[parts.Length - 1];
        parts = parts.TakeWhile((p, i) => i < parts.Length - 1).ToArray();
        string path2 = String.Join(".", parts);
        root = obj.GetPropertyValue<object>(path2);
    }

    var sourceType = root.GetType();
    var value = (TRet)sourceType.GetProperty(path).GetValue(root, null);
    return value;
}

推荐答案

如果您的意思是给出了具有一个参数的属性，请给我该值，例如：

If you mean "given an attribute that takes one parameter, give me that value", for example:

[DisplayName("abc")] <===== "abc"
[Browsable(true)] <===== true

然后通过新的 CustomAttributeData API在.NET 4.5中最简单：

then this is easiest in .NET 4.5, via the new CustomAttributeData API:

using System.ComponentModel;
using System.Reflection;

public static class Program
{
    static void Main()
    {
        PropertyInfo prop = typeof(Foo).GetProperty("Bar");
        var val = GetPropertyAttributes(prop, "DisplayName");
    }
    public static object GetPropertyAttributes(PropertyInfo prop, string attributeName)
    {
        // look for an attribute that takes one constructor argument
        foreach(CustomAttributeData attribData in prop.GetCustomAttributesData()) 
        {
            string typeName = attribData.Constructor.DeclaringType.Name;
            if(attribData.ConstructorArguments.Count == 1 &&
                (typeName == attributeName || typeName == attributeName + "Attribute"))
            {
                return attribData.ConstructorArguments[0].Value;
            }
        }
        return null;
    }
}

class Foo
{
    [DisplayName("abc")]
    public string Bar { get; set; }
}

这篇关于在不知道属性类型的情况下从属性和列表值获取属性值的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！