MVC 4刷新/清空/清除数据表

本文关键字：清除 数据表 清空 MVC 刷新 | 更新日期: 2023-09-27 18:09:58

有人能解释为什么Clear()或Dispose()不能刷新数据表记录集吗?

我在MVC 4项目中使用数据表，如var tbl = new DataTable()，这对检索数据很好，但出于某种原因，当我使用tbl.Clear()和tbl.Dispose()，然后尝试重用tbl时，它仍然有以前查询的记录集，为什么?

有人能让我知道如何冲洗/清除/清空以前的数据表记录集吗?

任何帮助都将非常感激:-)

请参见下面的示例代码:

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();
}

MVC 4刷新/清空/清除数据表

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 };

但是你必须用这个新命令来设置userRecord:

userRecord = new SqlDataAdapter(cmd);

下面是我修改的代码，它解决了我的问题。看起来我没有调用第二个存储过程，因此DataTable tbl没有被第二个数据集填充。

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();
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