C#.NET – Removing Duplicate Records From DataTable

Introduction

If a database table contains duplicate records, then it is easy to select unique records by using DISTINCT function, but when a .NET DataTable contains duplicate records, then there is no built-in function to remove or select unique records from a DataTable.

Objective

The main goal of this article is to create a function and remove and select unique records from a DataTable in C#.NET and return a clean and duplicate free DataTable.

Explanation

For removing duplicate records from DataTable, I have created the below function which needs two parameters, DataTable and Column Name. This function is searching for duplicate records in DataTable, given column name from second parameter and adding the row (record) in an ArrayList variable. Then, the record will be deleted from the datatable by running a loop on founded duplicate records.

DataTable containing duplicate records:

Function for Removing Duplicate Records from DataTable

/// <summary>
/// Remove duplicate records from data table
/// </summary>
/// <param name="table">DataTable for removing duplicate records</param>
/// <param name="DistinctColumn">Column to check for duplicate values or records</param>
/// <returns></returns>
public DataTable RemoveDuplicateRows(DataTable table, string DistinctColumn)
{
    try
    {
        ArrayList UniqueRecords = new ArrayList();
        ArrayList DuplicateRecords = new ArrayList();

        // Check if records is already added to UniqueRecords otherwise,
        // Add the records to DuplicateRecords
        foreach(DataRow dRow in table.Rows)
        {
            if (UniqueRecords.Contains(dRow[DistinctColumn]))
                DuplicateRecords.Add(dRow);
            else
                UniqueRecords.Add(dRow[DistinctColumn]);
        }

        // Remove duplicate rows from DataTable added to DuplicateRecords
        foreach (DataRow dRow in DuplicateRecords)
        {
            table.Rows.Remove(dRow);
        }

        // Return the clean DataTable which contains unique records.
        return table;
    }
    catch (Exception ex)
    {
        return null;
    }
}

Using the Function

It is very easy to use this function, all you need is to pass the datatable and column name parameters to the function and the function returns the cleaned datatable.

Example

DataTable DuplicateRecords = objDatabase.getTable("SQL Query");
DataTable UniqueRecords = RemoveDuplicateRows
(DuplicateRecords, "Column Name to check for duplicate records");

Clean and duplicate free DataTable using the above function:

Remarks

The above function selects the first record and deletes others if a duplicate record is found in DataTable.

Conclusion

By using this function, you will be able to clean your datatable from duplicate records.

Feel free to comment, suggest or give your feedback.