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Delete Duplicate entries in Datagrid / DataTable

Posted on 2004-09-01
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Last Modified: 2011-04-14
Hello dataGrid1 is bound to Products dataTable1

The format of the table is something like this after the user enters data into the dataGrid1 fields

colCategory   colDecription  colStyleNo
Top              Summer        123A
Blouse          Winter           456A
Top              Summer        123A

I need a function that will detect if the user has entered any duplicate entries (in this case the first and last entry are the same)?

How can I do this?
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Question by:auk_ie
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Expert Comment

by:eternal_21
ID: 11958804
You could put a restraint on the DataTable such that duplicate rows cannot be entered in the first place... would that work?
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Expert Comment

by:eternal_21
ID: 11958856
If that works, you can achieve that by sending your DataTable to this method:

  static void AddUniqueRowConstraint(System.Data.DataTable dataTable)
  {
    System.Data.DataColumn[] tableColumns = new System.Data.DataColumn[dataTable.Columns.Count];
    dataTable.Columns.CopyTo(tableColumns, 0);
    dataTable.Constraints.Add("NoDuplicateRows", tableColumns, false);
  }

Duplicate rows will not be possible!
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eternal_21 earned 500 total points
ID: 11960088
If that doesn't solve your problem, here are two functions.  The first will report true/false if the DataTable has duplicate records, the second will remove any duplicates from the Row collection:

    bool HasDuplicates(System.Data.DataTable dataTable)
    {
      System.Data.DataTable duplicateTable = dataTable.Clone();
      System.Data.DataColumn[] primaryKey = new System.Data.DataColumn[duplicateTable.Columns.Count];
      duplicateTable.Columns.CopyTo(primaryKey, 0);
      duplicateTable.PrimaryKey = primaryKey;

      foreach(System.Data.DataRow dataRow in dataTable.Rows)
        if(duplicateTable.Rows.Contains(dataRow.ItemArray))
          return true;
        else
          duplicateTable.Rows.Add(dataRow.ItemArray);
     
      return false;
    }

    void RemoveDuplicates(System.Data.DataTable dataTable)
    {
      System.Data.DataTable duplicateTable = dataTable.Clone();
      System.Data.DataColumn[] primaryKey = new System.Data.DataColumn[duplicateTable.Columns.Count];
      duplicateTable.Columns.CopyTo(primaryKey, 0);
      duplicateTable.PrimaryKey = primaryKey;
     
      System.Data.DataRow[] dataRows = new System.Data.DataRow[dataTable.Rows.Count];
      dataTable.Rows.CopyTo(dataRows, 0);
      foreach(System.Data.DataRow dataRow in dataRows)
        if(duplicateTable.Rows.Contains(dataRow.ItemArray))
          dataTable.Rows.Remove(dataRow);
        else
          duplicateTable.Rows.Add(dataRow.ItemArray);
    }
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Author Comment

by:auk_ie
ID: 11960326
Nice let look into both these solutions, I will reply tommorow
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Expert Comment

by:eternal_21
ID: 12011409
How did that work for you auk_ie?
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Author Comment

by:auk_ie
ID: 12011440
I actually got distracted for a bit, But I did get a chance to try out the first function, very cool
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