C# DataGridView: Long Text Truncated with “…” on the Left Side When the Column is Right-Aligned

Question

I have a question about the cell truncation (replaced with \"...\"):

How to display the replacement \"...\" on the left side of a cell when the column is right-align

Answer 1

It's definitely an unusual thing to do - but (like anything else) it can be done. It's a question of measuring the size of the string and comparing it with the size of the cell. (Note that I assume that the data is entered by a user. If you're databinding you basically have to consume other events.)

This works but might need some fine tuning:

public partial class Form1 : Form
{
    public Form1()
    {
        InitializeComponent();
        dataGridView1.Columns.Add("col1", "col1");
        dataGridView1.Columns[0].CellTemplate.Style.Alignment = DataGridViewContentAlignment.MiddleRight;
        dataGridView1.Columns.Add("col2", "col2");
        dataGridView1.Columns.Add("col3", "col3");

        dataGridView1.Rows.Add();
        dataGridView1.CellEndEdit += new DataGridViewCellEventHandler(dataGridView1_CellEndEdit);
        dataGridView1.ColumnWidthChanged += new DataGridViewColumnEventHandler(dataGridView1_ColumnWidthChanged);              
    }

    void dataGridView1_ColumnWidthChanged(object sender, DataGridViewColumnEventArgs e)
    {
        if (e.Column.Index == 0)
        {
            // We need to truncate everything again when the width changes
            foreach (DataGridViewRow row in dataGridView1.Rows)
            {
                RightTruncateText(row.Cells[0]);
            }
        }
    }

    void RightTruncateText(DataGridViewCell cell)
    {                        
        // check if the content is too long:
        using (Graphics g = Graphics.FromHwnd(this.Handle))
        {
            SizeF size = g.MeasureString((string)cell.Tag, dataGridView1.Font); // NOTE: using the tag

            if (size.Width > cell.Size.Width)
            {
                StringBuilder truncated = new StringBuilder((string)cell.Tag);

                truncated.Insert(0, "...");

                // Truncate the string until small enough (NOTE: not optimized in any way!)                        
                while (size.Width > cell.Size.Width)
                {
                    truncated.Remove(3, 1);
                    size = g.MeasureString(truncated.ToString(), dataGridView1.Font);
                }
                cell.Value = truncated.ToString();
            }
            else
            {
                cell.Value = cell.Tag;
            }
        }
    }

    void dataGridView1_CellEndEdit(object sender, DataGridViewCellEventArgs e)
    {
        if (e.ColumnIndex == 0)
        {
            // Save the value in the tag but show the truncated value
            DataGridViewCell cell = dataGridView1.Rows[e.RowIndex].Cells[e.ColumnIndex];
            cell.Tag = cell.Value; // Saving the actual state
            RightTruncateText(cell);
        }
    }
}