可不可以从datatable中选出某一列不重复的数据。

可以。
string myStr="";
for(int i=0;i<dg.Items.Count;i++)
{
  if(myStr.IndexOf(dg.Items[i].cells[你要的列].Text)<0)
  {
   myStr+=dg.Items[i].cells[你要的列].Text+",";
   }
}最后得到的myStr就是你需要的不重复的数据。
该程序没有经过测试，你自己再改改。

marysxj(小丸子) :
楼主用的是DataTable 啊. hdt(倦怠) ( ) :
能不能给解释一下.

DataTable.Select 方法  [C#]请参见
DataTable 类 | DataTable 成员 | System.Data 命名空间 | 代码：查询数据表 (Visual Basic) | C++ 托管扩展编程语言
C#C++JScriptVisual Basic全部显示
获取 DataRow 对象的数组。
重载列表
获取所有 DataRow 对象的数组。
受 .NET Framework 精简版的支持。
[Visual Basic] Overloads Public Function Select() As DataRow()
[C#] public DataRow[] Select();
[C++] public: DataRow* Select() [];
[JScript] public function Select() : DataRow[];
按照主键顺序（如果没有主键，则按照添加顺序）获取与筛选条件相匹配的所有 DataRow 对象的数组。
受 .NET Framework 精简版的支持。
[Visual Basic] Overloads Public Function Select(String) As DataRow()
[C#] public DataRow[] Select(string);
[C++] public: DataRow* Select(String*) [];
[JScript] public function Select(String) : DataRow[];
获取按照指定的排序顺序且与筛选条件相匹配的所有 DataRow 对象的数组。
受 .NET Framework 精简版的支持。
[Visual Basic] Overloads Public Function Select(String, String) As DataRow()
[C#] public DataRow[] Select(string, string);
[C++] public: DataRow* Select(String*, String*) [];
[JScript] public function Select(String, String) : DataRow[];
获取与排序顺序中的筛选器以及指定的状态相匹配的所有 DataRow 对象的数组。
受 .NET Framework 精简版的支持。
[Visual Basic] Overloads Public Function Select(String, String, DataViewRowState) As DataRow()
[C#] public DataRow[] Select(string, string, DataViewRowState);
[C++] public: DataRow* Select(String*, String*, DataViewRowState) [];
[JScript] public function Select(String, String, DataViewRowState) : DataRow[];
示例
[Visual Basic, C#] 以下示例使用筛选表达式和记录状态来返回 DataRow 对象的数组。
[Visual Basic, C#] 注意   此示例显示如何使用 Select 的一个重载版本。有关其他可用示例，请参阅单独的重载主题。
[Visual Basic]
Private Sub GetRowsByFilter()

    Dim customerTable As DataTable
    customerTable = new DataTable( "Customers" )    ' Add columns
    customerTable.Columns.Add( "id", GetType(Integer) )
    customerTable.Columns.Add( "name", GetType(String) )    ' Set PrimaryKey
    customerTable.Columns("id").Unique = true
    customerTable.PrimaryKey = new DataColumn() { customerTable.Columns("id") }    ' add ten rows
    Dim id As Integer
    For id = 1 To 10
        customerTable.Rows.Add( _
            new object() { id, string.Format("customer{0}", id) } )
    Next id
    customerTable.AcceptChanges()    ' add another ten rows
    For id = 11 To 20
        customerTable.Rows.Add( _
            new object() { id, string.Format("customer{0}", id) } )
    Next id    Dim strExpr As String
    Dim strSort As String

    strExpr = "id > 5"
    ' Sort descending by CompanyName column.
    strSort = "name DESC"
    ' Use the Select method to find all rows matching the filter.
    Dim foundRows As DataRow() = _
        customerTable.Select( strExpr, strSort, DataViewRowState.Added )

    PrintRows( foundRows, "filtered rows")    foundRows = customerTable.Select()
    PrintRows( foundRows, "all rows")
End SubPrivate Sub PrintRows( rows() As DataRow, label As String)
    Console.WriteLine( "\n{0}", label )
    If rows.Length <= 0 Then
        Console.WriteLine( "no rows found" )
        Exit Sub
    End If
    Dim r As DataRow
    Dim c As DataColumn
    For Each r In rows
        For Each c In r.Table.Columns
            Console.Write( "\t {0}", r(c) )
        Next c
        Console.WriteLine()
    Next r
End Sub
[C#]
private static void GetRowsByFilter()
{

    DataTable customerTable = new DataTable( "Customers" );
    // Add columns
    customerTable.Columns.Add( "id", typeof(int) );
    customerTable.Columns.Add( "name", typeof(string) );    // Set PrimaryKey
    customerTable.Columns[ "id" ].Unique = true;
    customerTable.PrimaryKey = new DataColumn[] { customerTable.Columns["id"] };    // Add ten rows
    for( int id=1; id<=10; id++ )
    {
        customerTable.Rows.Add(
            new object[] { id, string.Format("customer{0}", id) } );
    }
    customerTable.AcceptChanges();    // Add another ten rows
    for( int id=11; id<=20; id++ )
    {
        customerTable.Rows.Add(
            new object[] { id, string.Format("customer{0}", id) } );
    }    string strExpr;
    string strSort;

    strExpr = "id > 5";
    // Sort descending by column named CompanyName.
    strSort = "name DESC";
    // Use the Select method to find all rows matching the filter.
    DataRow[] foundRows =
        customerTable.Select( strExpr, strSort, DataViewRowState.Added );

    PrintRows( foundRows, "filtered rows" );    foundRows = customerTable.Select();
    PrintRows( foundRows, "all rows" );
}private static void PrintRows( DataRow[] rows, string label )
{
    Console.WriteLine( "\n{0}", label );
    if( rows.Length <= 0 )
    {
        Console.WriteLine( "no rows found" );
        return;
    }
    foreach( DataRow r in rows )
    {
        foreach( DataColumn c in r.Table.Columns )
        {
            Console.Write( "\t {0}", r[c] );
        }
        Console.WriteLine();
    }
}

但是那样做的话，就选不出那些重复的了。
我的意思是说要像sql语句中的distinct一样

这里有一个取distinct数据的方法.static DataTable SelectDistinct(string ReturnTableName, DataTable SourceTable, string ReturnFieldName, string AdditionalFilterExpression)
{
DataTable dt = new DataTable(ReturnTableName);
dt.Columns.Add(ReturnFieldName, SourceTable.Columns[ReturnFieldName].DataType);
object LastValue = null;
foreach (DataRow dr in SourceTable.Select("", ReturnFieldName))
{
if (LastValue == null || !(ColumnEqual(LastValue, dr[ReturnFieldName])))
{
LastValue = dr[ReturnFieldName];
dt.Rows.Add(new object[] { LastValue });
}
}
if (ds != null)
ds.Tables.Add(dt);
return dt;
}static 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
}

调试易

可不可以从datatable中选出某一列不重复的数据。

解决方案 »