Highlight duplicate rows in DataGridView using C# and VB.Net in Windows Application

Hi ryutenkan,

Please check this sample. now take its reference and correct your code.

Namespaces

C#

using System.Data;
using System.Drawing;
using System.Windows.Forms;

VB.Net

Imports System.Data
Imports System.Drawing
Imports System.Windows.Forms

Code

C#

private void Form1_Load(object sender, EventArgs e)
{
    DataTable dt = new DataTable();
    dt.Columns.Add("ID");
    dt.Columns.Add("Name");
    dt.Rows.Add("1", "Alpha");
    dt.Rows.Add("1", "Beta");
    dt.Rows.Add("1", "Alpha");
    dt.Rows.Add("2", "Alpha");
    dt.Rows.Add("2", "Beta");
    dt.Rows.Add("2", "Gamma");
    dt.Rows.Add("3", "Alpha");
    dt.Rows.Add("3", "Beta");
    dt.Rows.Add("3", "Beta");
    this.dataGridView1.DataSource = dt;
    for (int currentRow = 0; currentRow < dataGridView1.Rows.Count - 1; currentRow++)
    {
        int id = Convert.ToInt32(dataGridView1.Rows[currentRow].Cells[0].Value);
        string name = dataGridView1.Rows[currentRow].Cells[1].Value.ToString();
        for (int row = 0; row < dataGridView1.Rows.Count - 1; row++)
        {
            int idCompare = Convert.ToInt32(dataGridView1.Rows[row].Cells[0].Value);
            string nameCompare = dataGridView1.Rows[row].Cells[1].Value.ToString();
            if (currentRow != row)
            {
                if (id == idCompare && name == nameCompare)
                {
                    dataGridView1.Rows[currentRow].DefaultCellStyle.BackColor = Color.Green;
                    break;
                }
                else
                {
                    dataGridView1.Rows[currentRow].DefaultCellStyle.BackColor = Color.White;
                }
            }
        }
    }
}

VB.Net

Private Sub Form1_Load(ByVal sender As Object, ByVal e As EventArgs) Handles Me.Load
    Dim dt As DataTable = New DataTable()
    dt.Columns.Add("ID")
    dt.Columns.Add("Name")
    dt.Rows.Add("1", "Alpha")
    dt.Rows.Add("1", "Beta")
    dt.Rows.Add("1", "Alpha")
    dt.Rows.Add("2", "Alpha")
    dt.Rows.Add("2", "Beta")
    dt.Rows.Add("2", "Gamma")
    dt.Rows.Add("3", "Alpha")
    dt.Rows.Add("3", "Beta")
    dt.Rows.Add("3", "Beta")
    Me.dataGridView1.DataSource = dt
    For currentRow As Integer = 0 To dataGridView1.Rows.Count - 1 - 1
        Dim id As Integer = Convert.ToInt32(dataGridView1.Rows(currentRow).Cells(0).Value)
        Dim name As String = dataGridView1.Rows(currentRow).Cells(1).Value.ToString()
        For row As Integer = 0 To dataGridView1.Rows.Count - 1 - 1
            Dim idCompare As Integer = Convert.ToInt32(dataGridView1.Rows(row).Cells(0).Value)
            Dim nameCompare As String = dataGridView1.Rows(row).Cells(1).Value.ToString()
            If currentRow <> row Then
                If id = idCompare AndAlso name = nameCompare Then
                    dataGridView1.Rows(currentRow).DefaultCellStyle.BackColor = Color.Green
                    Exit For
                Else
                    dataGridView1.Rows(currentRow).DefaultCellStyle.BackColor = Color.White
                End If
            End If
        Next
    Next
End Sub

Screenshot