How to Merge DataGridView Cells in WinForms?

WinForms DataGridView Cell Merging: Complete Guide

The key to merging cells in WinForms's DataGridView is to find and handle duplicate values. Here are step-by-step instructions:

Find duplicate values

Define a helper method to compare cell values ​​for equality:

bool IsTheSameCellValue(int column, int row)
{
    DataGridViewCell cell1 = dataGridView1[column, row];
    DataGridViewCell cell2 = dataGridView1[column, row - 1];
    if (cell1.Value == null || cell2.Value == null)
    {
       return false;
    }
    return cell1.Value.ToString() == cell2.Value.ToString();
}

CellPainting

In the CellPainting event of DataGridView, adjust the border style of the merged cells:

private void dataGridView1_CellPainting(object sender, DataGridViewCellPaintingEventArgs e)
{
    e.AdvancedBorderStyle.Bottom = DataGridViewAdvancedCellBorderStyle.None;
    if (e.RowIndex < 0 || e.ColumnIndex < 0)
        return;
    if (IsTheSameCellValue(e.ColumnIndex, e.RowIndex))
    {
        e.AdvancedBorderStyle.Top = DataGridViewAdvancedCellBorderStyle.None;
    }
}

Cell formatting event (CellFormatting)

In the CellFormatting event, handle the formatting of merged cells:

private void dataGridView1_CellFormatting(object sender, DataGridViewCellFormattingEventArgs e)
{
    if (e.RowIndex == 0)
        return;
    if (IsTheSameCellValue(e.ColumnIndex, e.RowIndex))
    {
        e.Value = "";
        e.FormattingApplied = true;
    }
}

Form Loading

Disable automatic column generation:

private void Form1_Load(object sender, EventArgs e)
{
    dataGridView1.AutoGenerateColumns = false;
}

Through the above steps, you can merge cells in the DataGridView to achieve the desired data presentation effect.

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