c# DataTable與不同結(jié)構(gòu)實體類轉(zhuǎn)換的方法實例

2020-01-24 03:04:49

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供稿：網(wǎng)友

在實際開發(fā)過程中，或者是第三方公司提供的數(shù)據(jù)表結(jié)構(gòu)，與我們系統(tǒng)中的實體類字段不對應(yīng)，遇到這樣我們怎么處理呢？可能有人會說，在轉(zhuǎn)換時創(chuàng)建一個實體對象，對表里的數(shù)據(jù)逐行遍歷來實例化這個實體對象不就完了。的確沒錯，這方法可行，但是這個方法效率極低，遇到億萬數(shù)據(jù)的話那就要實例化億萬個對象，由此可見它的效率了。
先看一下我的實體類

復(fù)制代碼代碼如下:

/// <summary>
/// 具體的實體類，和數(shù)據(jù)表中不同
/// </summary>
public class Person
{
    [DataField("user_name")]//表示數(shù)據(jù)庫表里面的字段
    public string UserName { set; get; }//表示需要轉(zhuǎn)換成的字段
    [DataField("pass_word")]
    public string PassWord { set; get; }
}

具體在代碼中有注釋，下面是轉(zhuǎn)換類

復(fù)制代碼代碼如下:

[AttributeUsage(AttributeTargets.Property)]
public sealed class DataFieldAttribute : Attribute
{
    /// <summary>
    /// 表對應(yīng)的字段名
    /// </summary>
    public string ColumnName { set; get; }

    public DataFieldAttribute(string columnName)
    {
        ColumnName = columnName;
    }
}

public static class DataConvert<T> where T : new()
{
    /// <summary>
    /// 將DataRow行轉(zhuǎn)換成Entity
    /// </summary>
    /// <param name="dr"></param>
    /// <returns></returns>
    public static T ToEntity(DataRow dr)
    {
        T entity = new T();
        Type info = typeof(T);
        var members = info.GetMembers();
        foreach (var mi in members)
        {
            if (mi.MemberType == MemberTypes.Property)
            {
                //讀取屬性上的DataField特性
                object[] attributes = mi.GetCustomAttributes(typeof(DataFieldAttribute), true);
                foreach (var attr in attributes)
                {
                    var dataFieldAttr = attr as DataFieldAttribute;
                    if (dataFieldAttr != null)
                    {
                        var propInfo = info.GetProperty(mi.Name);
                        if (dr.Table.Columns.Contains(dataFieldAttr.ColumnName))
                        {
                            //根據(jù)ColumnName，將dr中的相對字段賦值給Entity屬性
                            propInfo.SetValue(entity,
                                              Convert.ChangeType(dr[dataFieldAttr.ColumnName], propInfo.PropertyType),
                                              null);
                        }

                    }
                }
            }
        }
        return entity;
    }

    /// <summary>
    /// 將DataTable轉(zhuǎn)換成Entity列表
    /// </summary>
    /// <param name="dt"></param>
    /// <returns></returns>
    public static List<T> ToList(DataTable dt)
    {
        List<T> list = new List<T>(dt.Rows.Count);
        foreach (DataRow dr in dt.Rows)
        {
            list.Add(ToEntity(dr));
        }
        return list;
    }
}

調(diào)用代碼：

復(fù)制代碼代碼如下:

DataTable dt = new DataTable();
dt.Columns.Add("user_name");
dt.Columns.Add("pass_word");//這是表中的字段，現(xiàn)在需要將它們轉(zhuǎn)換為具體的實體類實例
dt.Rows.Add("kingtiger","1");
dt.Rows.Add("wangbiao", "2");

var users = DataConvert<Person>.ToList(dt);
foreach (var user in users)
{
    Response.Write(user.UserName + "," + user.PassWord);
}

for (int i = 0; i < dt.Rows.Count; i++)
{
    Person p = DataConvert<Person>.ToEntity(dt.Rows[i]);
    Response.Write(p.UserName + "," + p.PassWord);
}