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How To Select Distinct Record From Dataset




using System;
using System.Data;
using System.Configuration;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;

/// <summary>
/// Summary description for DataSetHelper
/// </summary>
public class DataSetHelper
{
public DataSet ds;
public DataSetHelper(ref DataSet DataSet)
{
ds = DataSet;
}
public DataSetHelper()
{
ds = null;
}
private bool ColumnEqual(object A, object B)
{

// Compares two values to see if they are equal. Also compares DBNULL.Value.
// Note: If your DataTable contains object fields, then you must extend this
// function to handle them in a meaningful way if you intend to group on them.

if (A == DBNull.Value && B == DBNull.Value) // both are DBNull.Value
return true;
if (A == DBNull.Value || B == DBNull.Value) // only one is DBNull.Value
return false;
return (A.Equals(B)); // value type standard comparison
}
public DataTable SelectDistinct(string TableName, DataTable SourceTable, string FieldName)
{
DataTable dt = new DataTable(TableName);
dt.Columns.Add(FieldName, SourceTable.Columns[FieldName].DataType);

object LastValue = null;
foreach (DataRow dr in SourceTable.Select("", FieldName))
{
if (LastValue == null || !(ColumnEqual(LastValue, dr[FieldName])))
{
LastValue = dr[FieldName];
dt.Rows.Add(new object[] { LastValue });
}
}
if (ds != null)
ds.Tables.Add(dt);
return dt;
}


}


Default.aspx

<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Distinct.aspx.cs"
Inherits="Distinct" %>


<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
<title>Untitled Page</title>
</head>
<body>
<form id="form1" runat="server">
<div>
<asp:GridView ID="GridView1" runat="Server">
</asp:GridView>
</div>
</form>
</body>
</html>



Default.aspx.cs

using System;
using System.Data;
using System.Configuration;
using System.Collections;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;

public partial class Distinct : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
DataSetHelper dsHelper = new DataSetHelper();
dsHelper.SelectDistinct("Name", GetDataSource(), "Name");
GridView1.DataSource = dsHelper.SelectDistinct("Name", GetDataSource(), "Name");
GridView1.DataBind();




}
protected DataTable GetDataSource()
{

const string key = "MyDataSource";
DataTable dt = Session[key] as DataTable;

if (dt == null)
{

dt = new DataTable();
dt.Columns.Add("ID", typeof(int));

dt.Columns.Add("Name", typeof(string));
dt.Rows.Add("1", "first object");

dt.Rows.Add("2", "second object");
dt.Rows.Add("3", "second object");
dt.Rows.Add("4", "second object");
Session[key] = dt;

}

return dt;
}
}

Comments

  1. (from v in tdEmployees.AsEnumerable() select v).Distinct()

    ReplyDelete

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