从 IDataReader 映射时，我可以将 AutoMapper 配置为读取自定义列名称吗？

Question

用于映射配置的伪代码（如下）是不可能的，因为 lambda 只允许我们访问 IDataReader 类型，而在实际映射时，AutoMapper 将到达每个 IDataRecord 的每个“单元格”，而 IDataReader .Read() == true：

var mappingConfig = Mapper.CreateMap<IDataReader, IEnumerable<MyDTO>>();
mappingConfig.ForMember(
    destination => destination.???,
    options => options.MapFrom(source => source.???));

任何人都可以想出一种在运行时使用 AutoMapper 配置或仅满足以下要求的其他动态方法来执行此操作的方法。

要求是支持任何传入的 IDataReader ，其列名称可能与 MyDTO 的属性名称不匹配，并且没有我可以依赖的命名约定。相反，我们会要求用户在运行时通过 IDataReader.GetSchemaTable() 交叉引用预期的列名称与在 IDataReader 中找到的实际列名称。

Answer 1

我不知道 automapper，但我使用 ValueInjecter 将 datareader 映射到对象，如下所示

 while (dr.Read())
 {
    var o = new User();
    o.InjectFrom<DataReaderInjection>(dr);
    return o;
 }

： DataReaderInjection（类似于 Automapper 的 ValueResolver），

public class DataReaderInjection : KnownSourceValueInjection<IDataReader>
    {
        protected override void Inject(IDataReader source, object target, PropertyDescriptorCollection targetProps)
        {
            for (var i = 0; i < source.FieldCount; i++)
            {
                var activeTarget = targetProps.GetByName(source.GetName(i), true);
                if (activeTarget == null) continue;

                var value = source.GetValue(i);
                if (value == DBNull.Value) continue;

                activeTarget.SetValue(target, value);
            }
        }
    }

您可以使用它将值从 IDataReader 注入到任何类型的对象

---

ok, so according to your requirements, I guess it should be like this:

public class DataReaderInjection : KnownSourceValueInjection<IDataReader>
        {
            protected override void Inject(IDataReader source, object target, PropertyDescriptorCollection targetProps)
            {
                var columns = source.GetSchemaTable().Columns;
                for (var i = 0; i < columns.Count; i++)
                {
                    var c = columns[i];

                    var targetPropName = c.ColumnName; //default is the same as columnName

                    if (c.ColumnName == "Foo") targetPropName = "TheTargetPropForFoo";
                    if (c.ColumnName == "Bar") targetPropName = "TheTargetPropForBar";
                    //you could also create a dictionary and use it here

                    var targetProp = targetProps.GetByName(targetPropName);
                    //go to next column if there is no such property in the target object
                    if (targetProp == null) continue;

                    targetProp.SetValue(target, columns[c.ColumnName]);
                }
            }
        }

在这里我使用了 GetSchemaTable，就像你想要的:)

---

ok, if you want to pass some stuff to the injection, you can do it in many ways, here's how:

o.InjectFrom(new DataReaderInjection(stuff), dr);
//you need a constructor with parameters for the DataReaderInjection in this case

var ri = new DataReaderInjection();
ri.Stuff = stuff;
o.InjectFrom(ri, dr);
//you need to add a property in this case

这是一个提示（对于带参数的构造函数）

  public class DataReaderInjection : KnownSourceValueInjection<IDataReader>
     {
        private IDictionary<string, string> stuff;
        public DataReaderInjection(IDictionary<string,string> stuff)
        {
          this.stuff = stuff;
        }
                    protected override void Inject(
...