我不确定我是否理解您在使用 DataTable 时的限制，但是我过去在需要“刷新”DataTable 中的数据或使用不同的标准重新填充它时做过的一件事是创建一个从 DataTable 派生的新类其中包括对 DataAdapter 的引用，该引用带有最初用于填充 DataTable 的连接和选择信息。
例如，DataTable 子类可能类似于LazyDataTable下面的代码。请注意，我添加了几种访问行的不同方法。在查看本文末尾附近的PermissionSource主要代码后，它们可能会更有意义。另外，请注意，我并未包含与在每种情况下正确打开和关闭数据库连接相关的所有详细信息。您如何处理取决于您的数据库访问模型（例如连接池、共享连接等）。Program
//using System.Data.Common;
public class LazyDataTable : DataTable {
protected DbDataAdapter Adapter { get; set; }
public LazyDataTable(DbDataAdapter a) {
Adapter = a;
}
/// <summary>
/// Save changes back to the database, using the DataAdapter
/// </summary>
public void Update() {
Adapter.Update(this);
}
/// <summary>
/// Fill this datatable using the SelectCommand in the DataAdapter
/// The DB connection and query have already been set.
/// </summary>
public void Fill() {
Adapter.Fill(this);
}
/// <summary>
/// read and return one row at a time, using IEnumerable syntax
/// (this example does not actually add the row to this table,
/// but that can be done as well, if desired.
/// </summary>
public IEnumerable<DataRow> LazyReadRows() {
using (var reader = OpenReader()) {
//Get the schema from the reader and copy it to this table.
var schema = reader.GetSchemaTable();
var values = new object[schema.Columns.Count];
while (reader.Read()) {
reader.GetValues(values);
var row = schema.NewRow();
row.ItemArray = values;
yield return row;
}
}
}
/// <summary>
/// Fill one row at a time, and return the new row.
/// </summary>
public DataRow ReadRow() {
if (_reader == null || _reader.IsClosed)
_reader = OpenReader();
//Get the schema from the reader and copy it to this table.
if (this.Columns.Count == 0)
this.Columns.AddRange(_reader.GetSchemaTable().Columns.Cast<DataColumn>().ToArray());
if (!_reader.Read()) {
_reader.Dispose();
return null;
}
var values = new object[_reader.FieldCount];
_reader.GetValues(values);
return this.Rows.Add(values);
}
private DbDataReader _reader = null;
private DbDataReader OpenReader() {
OpenConnect();
return Adapter.SelectCommand.ExecuteReader();
}
private void OpenConnect() {
var cn = Adapter.SelectCommand.Connection;
if (cn.State == ConnectionState.Closed)
cn.Open();
}
/// <summary>
/// Change a Parameter in the SelectCommand, to filter which rows to retrieve.
/// </summary>
public void SetSelectParam(string name, object value) {
var selparams = Adapter.SelectCommand.Parameters;
selparams[name].Value = value;
}
}
然后您PermissionSource将创建一个LazyDataTable并适当地设置 DataAdapter（包括连接和 SELECT 命令）。它不会填充 DataTable，而是将其返回为空，稍后由应用程序代码填充。所以你PermissionSource可能类似于下面的代码。我以System.Data.OleDb数据对象为例，但您可以使用任何您想要的 ADO 提供程序。
interface ISource {
public DataTable Table { get; }
string UniqueName { get; }
}
public class PermissionSource : ISource {
/// <summary>
/// Loads a DataTable with all of the information to load it lazily.
/// </summary>
public DataTable Table {
get {
const string SELECT_CMD = "SELECT * FROM [Permissions] WHERE ([PermissionName] IS NULL OR [PermissionName]=@p1) AND [OtherProperty]=@p2";
var conn = new OleDbConnection("...ConnectionString...");
var selectCmd = new OleDbCommand(SELECT_CMD, conn);
selectCmd.Parameters.AddWithValue("p1", "PermissionName");
selectCmd.Parameters.AddWithValue("p2", 0);
var adapter = new OleDbDataAdapter(selectCmd);
var builder = new OleDbCommandBuilder(adapter); //used to generate the UPDATE and DELETE commands...
adapter.UpdateCommand = builder.GetUpdateCommand(); //etc.
//Do NOT fill the table here. Instead, let the caller fill it.
return new LazyDataTable(adapter);
}
}
public string UniqueName { get { return "Permission"; } }
}
PermissionSource您的主程序代码将使用LazyDataTable如下：
static class Program {
void GetPermissions() {
ISource permissionSource = SourceManager.Sources.
Where(s => "Permission".Equals(s.UniqueName)).First();
var table = permissionSource.Table as LazyDataTable;
table.SetSelectParam("PermissionName", "Admin");
//If you want to fill ALL rows in one step:
table.Fill();
// OR If you want to fill one row at a time, and add it to the table:
DataRow row;
while(null != (row = table.ReadRow())) {
//do something with each individual row. Exit whenever desired.
Console.WriteLine(row["PermissionName"]);
}
// OR If you prefer IEnumerable semantics:
DataRow row = table.LazyReadRows().FirstOrDefault(someValue.Equals(row["columnname"]));
//OR use foreach, etc. Rows are still ONLY read one at a time, each time IEnumerator.MoveNext() is called.
foreach (var row in table.LazyReadRows())
if (row["someColumn"] == "someValue")
DoSomething(row["anothercolumn"]);
}
}
您当然可以混合和匹配此处显示的 LazyDataTable 的各个部分，以在应用程序约束范围内准确实现您想要的。如果您可以切换到不同的共享数据模型当然会好得多，但是如果您必须从每个 Source 返回一个 DataTable，那么至少您可以在必要时通过子类化返回一个功能更强大的 DataTable，正如我所展示的这里。这允许您传回更多信息，您可以根据需要使用这些信息来填充表格。我仍然鼓励您查看 LinqToSQL，并可能尝试切换为简单地传回 DbDataReader 或类似于我在此处显示的 LazyDataTable 的其他对象，这将允许您自定义原始查询（例如，通过使用SetSelectParam方法）并且一次读取一行中的数据。
希望有帮助！