在我们的应用程序中我们使用类描述我们的业务对象，为我们产生一些报表之类的，那就依赖大量不同的对象，我们创建一个帮助方法来转换我们的业务对象，或是一个List的业务对象到DataTables.
由于数据库表中字段可为null,对应.net 2.0以后我们可用Nullable类型来实现，那当我们业务对象类中字段有null时，并需要转换为DataTable时，这个场景产生，你可能用到以下方法：
下面的代码是一个list对象(不支持处理复杂类型)返回一个描述对象的DataTable
////// Converts a Generic List into a DataTable /// /// /// ///private DataTable GetDataTable(IList list, Type typ) { DataTable dt = new DataTable(); // Get a list of all the properties on the object PropertyInfo[] pi = typ.GetProperties(); // Loop through each property, and add it as a column to the datatable foreach (PropertyInfo p in pi) { // The the type of the property Type columnType = p.PropertyType; // We need to check whether the property is NULLABLE if (p.PropertyType.IsGenericType && p.PropertyType.GetGenericTypeDefinition() == typeof(Nullable<>)) { // If it is NULLABLE, then get the underlying type. eg if "Nullable " then this will return just "int" columnType = p.PropertyType.GetGenericArguments()[0]; } // Add the column definition to the datatable. dt.Columns.Add(new DataColumn(p.Name, columnType)); } // For each object in the list, loop through and add the data to the datatable. foreach (object obj in list) { object[] row = new object[pi.Length]; int i = 0; foreach (PropertyInfo p in pi) { row[i++] = p.GetValue(obj, null); } dt.Rows.Add(row); } return dt; }
上面的代码的关键点：
- 用 PropertyType.IsGenericType 决定property是否是generic类型
- 用 ProprtyType.GetGenericTypeDefinition() == typeof(Nullable<>) 检测它是否是一个nullable类型
- 用 PropertyType.GetGenericArguments() 获取基类型。
下面让我们来应用一下：
public class Person{ public string Name { get; set; } public DateTime DateOfBirth { get; set; } public DateTime? DateOfDeath { get; set; }}public class Example{ public static DataTable RunExample() { Person edward = new Person() { Name = "Edward", DateOfBirth = new DateTime(1900, 1, 1), DateOfDeath = new DateTime(1990, 10, 15) }; Person margaret = new Person() { Name = "Margaret", DateOfBirth = new DateTime(1950, 2, 9), DateOfDeath = null }; Person grant = new Person() { Name = "Grant", DateOfBirth = new DateTime(1975, 6, 13), DateOfDeath = null }; List people = new List (); people.Add(edward); people.Add(margaret); people.Add(grant); DataTable dt = GetDataTable(people, typeof(Person)); return dt; }}将返回的DataTable像下面的内容:Name (string) DateOfBirth (DateTime) DateOfDeath (DateTime)Edward 1/1/1900 15/10/1990Margaret 9/2/1950 [NULL]Grant 13/6/1975 [NULL]