Question

有人可以解释为什么Clear()或Dispose()无法刷新DataTable记录集吗？

我在MVC 4项目中使用DataTable，如var tbl = new DataTable()这样可以很好地检索数据，但出于某些原因我使用tbl.Clear()和tbl.Dispose()然后尝试重用tbl它仍然具有上一个查询的记录集，为什么？

有人可以告诉我如何刷新/清除/清空以前的DataTable记录集吗？

非常感谢任何帮助： - ）

请参阅下面的示例代码：

string name = "";
string password = "";

var stringWriter = new StringWriter();
var writer = new XmlTextWriter(stringWriter) { Formatting = Formatting.Indented };    

var tbl = new DataTable();

string strConn = WebConfigurationManager.ConnectionStrings["TestConnection"].ToString();

var conn = new SqlConnection(strConn);
using (conn)
{
    conn.Open();
    var cmd = new SqlCommand("GetUserLoginID", conn) {CommandType = CommandType.StoredProcedure};
    cmd.Parameters.AddWithValue("@UID", uid);
    cmd.Parameters.AddWithValue("@BID", bId);

    var userRecord = new SqlDataAdapter(cmd);

    userRecord.Fill(tbl);
    conn.Close();

    if (tbl.Rows.Count > 0)
    {
        var row = tbl.Rows[0];

        name = row["Name"].ToString();
        password = row["Password"].ToString();
        code = row["Code"].ToString();
    }

    tbl.Clear();
    tbl.Dispose();

    cmd = new SqlCommand("GetUserDetails", conn) { CommandType = CommandType.StoredProcedure };
    cmd.Parameters.AddWithValue("@Code", code);
    cmd.Parameters.AddWithValue("@BID", bId);

    userRecord.Fill(tbl);

    if (tbl.Rows.Count > 0)
    {
        var row = tbl.Rows[0];

        writer.WriteStartDocument();
        writer.WriteStartElement("Root");
        writer.WriteElementString("BID", row["BID"].ToString());
        writer.WriteElementString("Name", name);

    }
    else
    {
        writer.WriteStartDocument();
        writer.WriteStartElement("Root");
        writer.WriteElementString("BID", "Error");
    }
    writer.WriteEndElement();
    writer.Flush();
    writer.Close();
}

Answer 1

似乎你总是使用相同的SqlDataAdapter。您创建了一个新命令：

cmd = new SqlCommand("GetUserDetails", conn) { CommandType = CommandType.StoredProcedure };

但你必须使用这个新命令设置userRecord：

userRecord = new SqlDataAdapter(cmd);

Answer 2

以下是我修改过的代码，它解决了我的问题。看来我没有调用第二个存储过程，因此DataTable tbl没有填充第二个数据集。

string name = "";
string password = "";

var stringWriter = new StringWriter();
var writer = new XmlTextWriter(stringWriter) { Formatting = Formatting.Indented };    

var tbl = new DataTable();

string strConn = WebConfigurationManager.ConnectionStrings["TestConnection"].ToString();

var conn = new SqlConnection(strConn);
using (conn)
{
    conn.Open();
    var cmd = new SqlCommand("GetUserLoginID", conn) {CommandType = CommandType.StoredProcedure};
    cmd.Parameters.AddWithValue("@UID", uid);
    cmd.Parameters.AddWithValue("@BID", bId);

    var userRecord = new SqlDataAdapter(cmd);

    userRecord.Fill(tbl);

    if (tbl.Rows.Count > 0)
    {
        var row = tbl.Rows[0];

        name = row["Name"].ToString();
        password = row["Password"].ToString();
        code = row["Code"].ToString();
    }

    tbl.Clear();

    cmd = new SqlCommand("GetUserDetails", conn) { CommandType = CommandType.StoredProcedure };
    cmd.Parameters.AddWithValue("@Code", code);
    cmd.Parameters.AddWithValue("@BID", bId);

    userRecord = new SqlDataAdapter(cmd);

    userRecord.Fill(tbl);

    if (tbl.Rows.Count > 0)
    {
        var row = tbl.Rows[0];

        writer.WriteStartDocument();
        writer.WriteStartElement("Root");
        writer.WriteElementString("BID", row["BID"].ToString());
        writer.WriteElementString("Name", name);

    }
    else
    {
        writer.WriteStartDocument();
        writer.WriteStartElement("Root");
        writer.WriteElementString("BID", "Error");
    }
    writer.WriteEndElement();
    writer.Flush();
    writer.Close();

    conn.Close();
}
tbl.Dispose();

MVC 4 Flush / Empty / Clear DataTable

2 个答案: