從數據表中刪除重複條目的最佳方法

Question

從數據表中刪除重複條目的最佳方法是什麼？

Answer 1

刪除重複

public DataTable RemoveDuplicateRows(DataTable dTable, string colName) 
{ 
    Hashtable hTable = new Hashtable(); 
    ArrayList duplicateList = new ArrayList(); 

    //Add list of all the unique item value to hashtable, which stores combination of key, value pair. 
    //And add duplicate item value in arraylist. 
    foreach (DataRow drow in dTable.Rows) 
    { 
     if (hTable.Contains(drow[colName])) 
     duplicateList.Add(drow); 
     else 
     hTable.Add(drow[colName], string.Empty); 
    } 

    //Removing a list of duplicate items from datatable. 
    foreach (DataRow dRow in duplicateList) 
     dTable.Rows.Remove(dRow); 

    //Datatable which contains unique records will be return as output. 
     return dTable; 
} 

這裏鏈接下面

http://www.dotnetspider.com/resources/4535-Remove-duplicate-records-from-table.aspx

http://www.dotnetspark.com/kb/94-remove-duplicate-rows-value-from-datatable.aspx

對於刪除重複在柱

http://dotnetguts.blogspot.com/2007/02/removing-duplicate-records-from.html

Answer 2

做dtEmp在當前工作的DataTable：

DataTable distinctTable = dtEmp.DefaultView.ToTable(/*distinct*/ true); 

很高興。

Answer 3

使用AsEnumerable().Distinct()

private DataTable RemoveDuplicatesRecords(DataTable dt) 
{ 
    //Returns just 5 unique rows 
    var UniqueRows = dt.AsEnumerable().Distinct(DataRowComparer.Default); 
    DataTable dt2 = UniqueRows.CopyToDataTable(); 
    return dt2; 
} 

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Answer 4

這篇文章是關於多個列的基礎上只讀取數據，從表Distincts行繼承人方便，快捷的方式。

Public coid removeDuplicatesRows(DataTable dt) 
{ 
    DataTable uniqueCols = dt.DefaultView.ToTable(true, "RNORFQNo", "ManufacturerPartNo", "RNORFQId", "ItemId", "RNONo", "Quantity", "NSNNo", "UOMName", "MOQ", "ItemDescription"); 
} 

您需要調用此方法，並且需要爲數據表賦值。 在上面的代碼中，我們將RNORFQNo，PartNo，RFQ id，ItemId，RNONo，QUantity，NSNNO，UOMName，MOQ和項目描述作爲Column列出，我們希望獲得不同的值。

Answer 5

/* To eliminate Duplicate rows */ 
    private void RemoveDuplicates(DataTable dt) 
    { 

     if (dt.Rows.Count > 0) 
     { 
      for (int i = dt.Rows.Count - 1; i >= 0; i--) 
      { 
       if (i == 0) 
       { 
        break; 
       } 
       for (int j = i - 1; j >= 0; j--) 
       { 
        if (Convert.ToInt32(dt.Rows[i]["ID"]) == Convert.ToInt32(dt.Rows[j]["ID"]) && dt.Rows[i]["Name"].ToString() == dt.Rows[j]["Name"].ToString()) 
        { 
         dt.Rows[i].Delete(); 
         break; 
        } 
       } 
      } 
      dt.AcceptChanges(); 
     } 
    } 

Answer 6

有一種使用Linq GroupBy方法的簡單方法。

var duplicateValues = dt.AsEnumerable() 

     .GroupBy(row => row[0]) 

     .Where(group => (group.Count() == 1 || group.Count() > 1)) 

     .Select(g => g.Key); 



foreach (var d in duplicateValues) 

     Console.WriteLine(d); 

• 多見於：http://www.dotnetlines.com/Blogs/tabid/85/EntryId/49/Remove-duplicate-rows-from-a-DataTable-using-LINQ.aspx

Answer 7

一個簡單的方法是：

var newDt= dt.AsEnumerable() 
       .GroupBy(x => x.Field<int>("ColumnName")) 
       .Select(y => y.First()) 
       .CopyToDataTable(); 

Answer 8

完全不同的行：

public static DataTable Dictinct(this dt) => dt.DefaultView.ToTable(true); 

鮮明由特定行（一個或多個）（注意，在「distinctCulumnNames」中提到的列將在結果DataTable退還）：

public static DataTable Dictinct(this dt, params string[] distinctColumnNames) => 
dt.DefaultView.ToTable(true, distinctColumnNames); 

通過特定的列中不同（保持在給定的數據表中的所有列）：

public static void Distinct(this DataTable dataTable, string distinctColumnName) 
{ 
    var distinctResult = new DataTable().Merge(
      dataTable.AsEnumerable() 
        .GroupBy(row => row.Field<object>(distinctColumnName)) 
        .Select(group => group.First()) 
        .CopyToDataTable() 
      ); 

    if (distinctResult.DefaultView.Count < dataTable.DefaultView.Count) 
    { 
     dataTable.Clear(); 
     dataTable.Merge(distinctResult); 
     dataTable.AcceptChanges(); 
    } 
} 

Answer 9

可以使用一個DataTable的DefaultView.ToTable方法來做這樣的過濾（適應C＃）：

Public Sub RemoveDuplicateRows(ByRef rDataTable As DataTable) 
    Dim pNewDataTable As DataTable 
    Dim pCurrentRowCopy As DataRow 
    Dim pColumnList As New List(Of String) 
    Dim pColumn As DataColumn 

    'Build column list 
    For Each pColumn In rDataTable.Columns 
     pColumnList.Add(pColumn.ColumnName) 
    Next 

    'Filter by all columns 
    pNewDataTable = rDataTable.DefaultView.ToTable(True, pColumnList.ToArray) 

    rDataTable = rDataTable.Clone 

    'Import rows into original table structure 
    For Each pCurrentRowCopy In pNewDataTable.Rows 
     rDataTable.ImportRow(pCurrentRowCopy) 
    Next 
End Sub