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How will get distinct values from datatable

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how i will get disctinct values , max and min from datatable

the code is below

dim dt as datatable
Dim drt() As DataRow
drt = dt.Select("distinct Roomtype")

getting error. says that 'System.Data.SyntaxErrorException: Syntax error: Missing operand after 'Roomtype' operator'

datatable contins values
i want the distinct roomtype from datatable
how i will get these values



Author: Mohan01 Mar 2004 Member Level: Silver   Points : 2

use these two functions to select distinct

private bool ColumnEqual(object A, object B)

if ( A == DBNull.Value && B == DBNull.Value )
return true;
if ( A == DBNull.Value || B == DBNull.Value )
return false;
return ( A.Equals(B) );


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)
return dt;

calling code

// your dataset code

DataTable dt=SelectDistinct("[tbl name]", ds.tables["table name"],"[distinct field name]")

//datatable dt now will contain distinct values

refer to link;EN-US;326176

Author: Cuckoo John Joseph05 Mar 2004 Member Level: Gold   Points : 2

A Simple Method to Get the Distinct Values.

Use this method.

Parameters :

Datatable from which the distinct values has to be fetched
colName is the name of the column for the distinct values.

so u can call like this.

object[] distinctRoomType = GetDistinctValues(dt,"Roomtype");

Here is the method definition.

public object[] GetDistinctValues(DataTable dtable,string colName)
Hashtable hTable = new Hashtable();
foreach(DataRow drow in dtable.Rows)
object[] objArray = new object[hTable.Keys.Count];
return objArray;

Cheers !

Author: geekman15 Nov 2005 Member Level: Bronze   Points : 2

I found this posting very helpful but the function supplied is too slow because it is designed to throw errors so I thought I would add my own varaition of the c# code:

public object[] GetDistinctValues(DataTable dtable, string colName)
Hashtable hTable = new Hashtable();
foreach (DataRow drow in dtable.Rows)
hTable.Add(drow[colName], string.Empty);
object[] objArray = new object[hTable.Keys.Count];
hTable.Keys.CopyTo(objArray, 0);
return objArray;

Author: suresh24 Aug 2007 Member Level: Bronze   Points : 2

Hi friends you may find this useful....

public DataRow[] GetDistinctRows(DataTable drows, string colName)
DataRow[] objArray = null;
if (drows != null && colName != null && colName != string.Empty)
Hashtable hTable = new Hashtable();
List<DataRow> distinctRows = new List<DataRow>();

foreach (DataRow drow in drows.Rows)
if (!hTable.ContainsKey(drow[colName].ToString()))
hTable.Add(drow[colName].ToString(), string.Empty);
objArray = new DataRow[distinctRows.Count];
return objArray;

Author: Ananda Babu Karthikeyan11 Feb 2008 Member Level: Silver   Points : 2

hello Martin,
Try this code. u'll get distinct table from ur original table(dtTemp).

 dim dt as datatable
Dim dtTemp As DataTable

Calippus Tech (India) Pvt. Ltd.

Author: chinnu14 Feb 2008 Member Level: Bronze   Points : 2

I think the above answer holds true only for framework 2.0 onwards.

People on earlier frameworks can use the following logic. Loop thru the table using-
for each dr as dataRow in"",columnName)
Keep adding the row to a dummy table(clone of original) when you see a change in the row(columnName) value.

Simple! I think using a hashtable will only slow up things.

Author: Mr.Rajesh21 Feb 2008 Member Level: Gold   Points : 2

"Select Distinct from Table";
this query will give u distinct table;

Author: Ananda Babu Karthikeyan21 Feb 2008 Member Level: Silver   Points : 2

hello rajesh ur code will not help. for this

Author: Sujit Kumar28 Aug 2008 Member Level: Gold   Points : 4

you can get distinct rows from dataset/datatable
DataSet ds=new DataSet();
//code to fill dataset from database.

DataTable dt=new DataTable();
//here true means you want distict result.

Author: Gopikrishna16 Feb 2009 Member Level: Bronze   Points : 3

The above codes need to be slightly modified. They all specify the column name as a string, where as the 'ToTable' method accepts a array of column names.

The code should be,
DataTable dt1=new DataTable();
DataTable dt2=new DataTable();

dt2=dt1.DefaultView.ToTable(true,new string [1]{"columnName"});