Question

问题是：如果我有MyConvertDataRowToEntity（DataRow行）我从类型Parent调用T对象，在内部我用desendant类型调用相同的函数Child我应该如何传递DataRow参数？调用MakeGenericMethod的Invoke时会产生问题。是否将类型更改为DataSet，字符串和字符串类型。没运气。（我认识到列对象中的子对象bu前缀 - PrefixDataColumn）

public static T MyConvertDataRowToEntity<T>(DataRow row ) where T : class, new()
    {

        Type objType = typeof(T);
        Type parentObjType = typeof(T);
        T obj = Activator.CreateInstance<T>(); //hence the new() contsraint
        PropertyInfo propertyGenericType = null;
        object childInstance = null;
        PropertyInfo property;
        string childColumnName = string.Empty ;
        foreach (DataColumn column in row.Table.Columns)
        {
            column.ColumnName = column.ColumnName.Replace("_", "");

            string PrefixDataColumn;
            if (column.ColumnName.IndexOf(".") > (-1))
            {
                ///gets the prefix that is the same as child entity name
                PrefixDataColumn = column.ColumnName.Substring(0, column.ColumnName.IndexOf("."));
                ///the column name in the child
                int length = column.ColumnName.Length - 1;
                int start = column.ColumnName.IndexOf(".") + 1;
                childColumnName = column.ColumnName.Substring(column.ColumnName.IndexOf(".") + 1);
                propertyGenericType = objType.GetProperty(PrefixDataColumn,
                                    BindingFlags.Public | BindingFlags.Instance | BindingFlags.IgnoreCase | BindingFlags.FlattenHierarchy);
                parentObjType = objType;
                if (propertyGenericType != null)
                {
                    Type childType = propertyGenericType.PropertyType;
                    objType = childType;
                    childInstance = Activator.CreateInstance(propertyGenericType.PropertyType);


                    // get the get method for the property
                    MethodInfo method = propertyGenericType.GetGetMethod(true);
                    // get the generic get-method generator 
                    MethodInfo genericHelper = typeof(DataUtil).GetMethod("MyConvertDataRowToEntity", BindingFlags.Public | BindingFlags.Static);

                    List<Type> signature = new List<Type>();
                    // first type parameter is type of target object
                    signature.Add(childType);

                    //next parameters are real types of method arguments
                    foreach (ParameterInfo pi in genericHelper.GetParameters())
                    {
                        signature.Add(pi.ParameterType);
                    }

                    // last parameters are known types of method arguments
                    signature.AddRange(typeof(T).GetGenericArguments());

                    // reflection call to the generic get-method generator to generate the type arguments
                    //MethodInfo constructedHelper = genericHelper.MakeGenericMethod(signature.ToArray());

                    // reflection call to the generic get-method generator to generate the type arguments
                    MethodInfo constructedHelper = genericHelper.MakeGenericMethod(childType );

                    // now call it. The null argument is because it's a static method.
                    object ret = constructedHelper.Invoke(null, new object[] { method });

                   // object myObj =  method.Invoke(null, row);
                   //// property.SetValue(obj, MyConvertDataRowToEntity<childInstance>(DataRow row),null);
                   // childInstance = DataUtil.GetMethod("MyConvertDataRowToEntity").MakeGenericMethod(childType); //MyConvertDataRowToEntity<object>(row); 

                    //childType initializedChild = ;
                    //property.SetValue(obj, value, null);
                    //objType = parentObjType;
                }
                else
                {
                    continue; 
                }
            }


        }
        return obj;
    }

获取此错误： “System.Reflection.RuntimeMethodInfo”类型的对象无法转换为“System.Data.DataRow”类型。

有没有解决方案？

P.S。尽可能地缩小代码范围。

如何使用desedant类型重新调用Method并传递datarow？

Answer 1

错误的原因是因为您正在调用MyConvertDataRowToEntity<ChildType>，而是将属性的getaccessor methodinfo作为参数传递而不是仅包含那些字段的数据行。

如果您想继续使用当前使用的代码处理逻辑，则需要构建一个新的数据行，其中包含您想要的字段（带有前缀和“。”），从列名的开头删除。

或者你可以创建一个辅助方法，接受一个列名，源对象，它只是更新了值。

static void UpdateItemProperty<T>(T item, string columnName, object rowValue) {
  var prefixColumn=columnName.IndexOf(".")==-1 ? columnName : columnName.Split(".")[0];
  var pi = typeof(T).GetProperty(prefixColumn // Add your binding flags);
  // if pi==null then there is an error...
  if (column.ColumnName.IndexOf(".") == (-1)) { // No Nesting
    pi.SetValue(item,rowValue);
    return;
  }
  // Nesting 
  var child=pi.GetValue(item);
  if (child==null) {
        // Logic here to get childs type and create an instance then call pi.SetValue with child
  }
  var remainder=string.Join(',',columnName.Split(".").Skip(1).ToArray());
  // make your generic method info for UpdateItemProperty with pi.PropertyType into mi
  mi.Invoke(null,new object[] { child,remainder,value };
}

使用DataRow参数递归调用泛型函数 - MakeGenericMethod失败

1 个答案: