// doing the same thing using  NET 2.0's DataView
[Test]
public void SelectDistinct_BasicTestUsingDataView()
{

    // will create a datatable with 45 rows.. with 9 distinct values
    // ie 10 + 9 + 8 + 7 + 6 + ... + 2 + 1
    DataTable Sourcedt = CreateTestDataTable(9);
    // make sure there are 45 rows in the table.. unit test the unit test
    Assert.AreEqual(45, Sourcedt.Rows.Count);

    DataView distinctTable = new DataView(Sourcedt);
    distinctTable.ToTable(true, new[] { "TestCol" });
    // No go ask for the distinct values
    DataTable resultdt = distinctTable.ToTable(/*distinct*/true, /*ColNames As array*/ new[] { "TestCol" });

    // make sure there are 9 distinct values 
    Assert.AreEqual(9, resultdt.Rows.Count);
}

// Create a DataTable with a single Column which contains non unique test string data   
// if you pass 3 into the function you will get:<br>
// Test3
// Test3
// Test3
// Test2
// Test2
// Test1
// The order is inverse to ensure the data is not asending 
private DataTable CreateTestDataTable(int NumberOfDistinctValues)
{
    DataTable result = new DataTable();
    result.Columns.Add("TestCol", typeof(System.String));
    for (int i = NumberOfDistinctValues; i >= 1; i--)
    {
        for (int j = 0; j < i; j++)
        {
            result.Rows.Add(new object[] { string.Format("Test{0}", i.ToString())});
        }
    }
    result.AcceptChanges();
    return result;
}



// This is the basic primary test for the function..
// it tests that the distinct works as expected and that the results are returned in ascending order as expected
[Test]
public void SelectDistinct_BasicTest()
{
    // will create a datatable with 45 rows.. with 10 distinct values
    // ie 10 + 9 + 8 + 7 + 6 + ... + 2 + 1
    DataTable Sourcedt = CreateTestDataTable(9);
    // make sure there are 45 rows in the table.. unit test the unit test
    Assert.AreEqual(45, Sourcedt.Rows.Count);

    // No go ask for the distinct values
    DataTable Resultdt = DataHelper.SelectDistinct(Sourcedt, "TestCol");
    // make sure there are 9 distinct values 
    Assert.AreEqual(9, Resultdt.Rows.Count);
    // Now make sure those values have been returned in ascending order
    for(int i = 1; i <= 9; i++)
    {
        Assert.AreEqual(string.Format("Test{0}", i), Resultdt.Rows[i - 1][0].ToString());
    }
}

// This is the basic primary test for the function..
// it tests that the distinct works as expected and that the results are returned in ascending order as expected
[Test]
public void SelectDistinct_BasicTestWithNullValues()
{
    // will create a datatable with 45 rows.. with 10 distinct values
    // ie 10 + 9 + 8 + 7 + 6 + ... + 2 + 1
    DataTable Sourcedt = CreateTestDataTable(9);
    Sourcedt.Rows.Add(new object[] {DBNull.Value});
    Sourcedt.Rows.Add(new object[] {null});

    // make sure there are 45 rows in the table.. unit test the unit test
    Assert.AreEqual(47, Sourcedt.Rows.Count);

    // No go ask for the distinct values
    DataTable Resultdt = DataHelper.SelectDistinct(Sourcedt, "TestCol");
    // make sure there are 9 distinct values 
    Assert.AreEqual(10, Resultdt.Rows.Count);
    // Now make sure those values have been returned in ascending order
    for (int i = 2; i <= 10; i++)
    {
        Assert.AreEqual(string.Format("Test{0}", i-1), Resultdt.Rows[i - 1][0].ToString());
    }
}


// tests the fucntion with a large dataset.. ie over a million rows.. 
// 
[Test]
public void SelectDistinct_BasicTestWithLargeAmountOfData()
{
    // will create a datatable with over a million rows ie 1125750 rows.. with 1500 distinct values
    // ie 1500 + 1499 +  ... + 2 + 1
    DataTable Sourcedt = CreateTestDataTable(1500);
    // make sure there are 1125750 rows in the table.. unit test the unit test
    Assert.AreEqual(1125750, Sourcedt.Rows.Count);
    DateTime StartTime = DateTime.Now;
    DataTable Resultdt = DataHelper.SelectDistinct(Sourcedt, "TestCol");
    TimeSpan ts = StartTime.Subtract(DateTime.Now);
    Assert.LessOrEqual(ts.TotalSeconds, 5);
    Assert.AreEqual(1500, Resultdt.Rows.Count);
}

[Test]
public void SelectDistinct_BasicTestWithEmptyDataTable()
{
    DataTable result = new DataTable();
    result.Columns.Add("TestCol", typeof(System.String));
    result.AcceptChanges();
    DataTable Resultdt = DataHelper.SelectDistinct(result, "TestCol");
    Assert.AreEqual(0, Resultdt.Rows.Count);
}

[Test]
public void SelectDistinct_BasicTestWithBadColName()
{
    DataTable result = new DataTable();
    result.Columns.Add("TestCol", typeof(System.String));
    result.AcceptChanges();
    try
    {
        DataTable Resultdt = DataHelper.SelectDistinct(result, "TestCol2");
    }
    catch (DataException ex)
    {
        // expected exception.. 
        Assert.AreEqual("Column Name TestCol2 Does not exist in SourceTable", ex.Message);
    }
}