如何添加属性级别的属性在运行时映射ColumnAttribute？ [英] How to add property-level Attribute to map ColumnAttribute at runtime?

问题描述

从这个<一个href=\"http://stackoverflow.com/questions/12143650/how-to-add-property-level-attribute-to-the-typedescriptor-at-runtime/\">question我们已实施相应的属性的ColumnAttribute关联，但是当LINQ到SQL试图将此属性映射到列这是行不通的。

From this question we have implemented the ColumnAttribute association with the corresponding property, but when Linq to SQL tries to map this property to a Column it doesn't work.

我们的财产和映射code（从另一个问题）：

Our property and mapping code(from the other question):

    public System.Xml.Linq.XElement Name {
        get {
            return this.name;
        }
        set {
            this.OnNameChanging(value);
            this.SendPropertyChanging();
            this.name = value;
            this.SendPropertyChanged("Name");
            this.OnNameChanged();
        }
    }

        System.Data.Linq.Mapping.ColumnAttribute columnAttribute = new System.Data.Linq.Mapping.ColumnAttribute();
        columnAttribute.Name = "Name";
        columnAttribute.Storage = "name";
        columnAttribute.DbType = "Xml NOT NULL";
        columnAttribute.CanBeNull = false;
        columnAttribute.UpdateCheck = System.Data.Linq.Mapping.UpdateCheck.Never;

        PropertyOverridingTypeDescriptor propertyOverrideTypeDescriptor = new PropertyOverridingTypeDescriptor(TypeDescriptor.GetProvider(typeof(ClassToMap)).GetTypeDescriptor(typeof(ClassToMap)));
        PropertyDescriptor pd = TypeDescriptor.GetProperties(typeof(ClassToMap)).Cast<PropertyDescriptor>().ToArray().Where(prop => prop.Name == "Name").FirstOrDefault();

        PropertyDescriptor pd2 = TypeDescriptor.CreateProperty(
            typeof(ClassToMap).GetType(),
            pd, // base property descriptor to which we want to add attributes
            // The PropertyDescriptor which we'll get will just wrap that
            // base one returning attributes we need.
            columnAttribute
            // this method really can take as many attributes as you like, not just one
        );

        propertyOverrideTypeDescriptor.OverrideProperty(pd2);
        TypeDescriptor.AddProvider(new TypeDescriptorOverridingProvider(typeof(ClassToMap)), typeof(ClassToMap));

不知道如何刷新表映射？

Any idea how to refresh the table mapping?

推荐答案

反射不使用类型描述符。您的测试很可能获得通过，因为另一个属性添加到code类。

Reflection does not utilize type descriptors. Your test probably passed because another attribute is added to a class in code.

有就是改变的LINQ to SQL类映射在飞行的方法。诀窍是一个XML映射文件添加到资源，当你创建一个数据上下文中使用它。当你的XML数据加载到内存中，可以根据您的需求决定修改映射。该解决方案在这里详细的描述：<一href=\"http://social.msdn.microsoft.com/Forums/en-US/f5e0af64-0057-4498-998b-70db656a0e9f/linq-to-sql-using-dynamic-tables\"相对=nofollow> LINQ到使用动态表的SQL

There is a way to change LINQ to SQL classes mapping on the fly. The trick is to add a XML mapping file to resources and use it when you create a data context. When you load XML data into memory, you can modify mappings as your needs dictate. This solution was described in detail here: Linq to sql using dynamic tables

在code片断：

foreach (XElement col in xe.Descendants().Where(e => e.Name.LocalName == "Column")) {
    XAttribute name = col.Attributes().FirstOrDefault(a => a.Name.LocalName == "Name" && a.Value == "CategoryName");
    if (name != null)
        name.Value = "Name";
}

这篇关于如何添加属性级别的属性在运行时映射ColumnAttribute？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！