How do write a generic function that takes a datarow and fill an object's properties?

问题

I have some function like

private static UserInfo FillUserInfoFromDataRow(DataRow dr)
{

     UserInfo user = new UserInfo();

     user.UserID = (int) dr["UserID"];
     user.UserName = (int) dr["UserName"];
     user.ProjectID = (int) dr["ProjectID"];
     user.ClassID = (int) dr["ClassID"];
     ..............

     return user;
}

I'd like to write some generic function like private static T FillEntityInfoFromDataRow(DataRow dr), that will treat analogous types ProjectInfo, JobInfo, etc.

I can get all columns names of the DataRow parameter, but I don't know how to get all the appropriate fields of the generic T type and how to do appropriate casting. Is it some way to do this job? Thanks!

Ilan.

回答1:

Its better to make use of reflection there are no of example avaible on google to do this this.

Check the below example

namespace MyNamespace.Data
{
    class Converter
    {
        public static void Fill(object LogicObject, DataRow Row)
        {
            Dictionary<string, PropertyInfo> props = new Dictionary<string,PropertyInfo>();
            foreach (PropertyInfo p in LogicObject.GetType().GetProperties())
                props.Add(p.Name, p);
            foreach (DataColumn col in Row.Table.Columns)
            {
                string name = col.ColumnName;
                if (Row[name] != DBNull.Value && props.ContainsKey(name))
                {
                    object item = Row[name];
                    PropertyInfo p = props[name];
                    if (p.PropertyType != col.DataType)
                        item = Convert.ChangeType(item, p.PropertyType);
                    p.SetValue(LogicObject, item, null);
                }
            }

        }
    }
}

Check the full blog post : http://kasey-jo.blogspot.com/2009/04/using-reflection-to-fill-business-layer.html

回答2:

I use this, which is sort of like what you need:

EDITED thanks to Heinzi

    public virtual void LoadDataRow(DataRow drow, params string[] parameters)
    {
        this.LoadDataRow(drow);
        foreach (string property in parameters)
        {
            try
            {
                if (drow[property] != null)
                {
                    PropertyInfo pi = this.GetType().GetProperty(property);
                    if (pi != null && drow.Table.Columns.Contains(property))
                    {
                        pi.SetValue(this, drow[property], null);
                    }
                }
            }
            catch { throw; }
        }
    }

In your case though, you might want to loop through th eproperty collection of your object first, and try to load from your dataset, but th eabove code should get you started.

EDIT

Found this on MSDN:

System.Reflection.PropertyInfo[] p = MyObject.GetType.GetProperties();
foreach(System.Reflection.PropertyInfo prop in p)
{
  ....
}

回答3:

Delegate this functionality to each specific class itself by declaring abstarct method in base class. BTW, I suggest to name this method like CreateFromDataRow()

abstract class InfoBase
{
    public abstract InfoBase CreateFromDataRow(DataRow dr);
}

abstract class InfoBase<T>
{
    public abstract T CreateFromDataRow(DataRow dr);
}

来源：https://stackoverflow.com/questions/6690501/how-do-write-a-generic-function-that-takes-a-datarow-and-fill-an-objects-proper

标签

.net

data-binding

reflection