Column as a LinkButton

You can achieve this by handling the RowDataBound event of the GridView control and converting the text of the cell to a LinkButton control. Then, you can add a JavaScript function to the OnClick attribute of the LinkButton to open the modal popup without a postback.

Here's an example code:

protected void GridView1_RowDataBound(object sender, GridViewRowEventArgs e)
{
    if (e.Row.RowType == DataControlRowType.DataRow)
    {
        // Get the value of the cell you want to convert to a LinkButton
        // assuming the first column contains the value you want to convert
        string cellValue = e.Row.Cells[0].Text; 
        
        // Create a new LinkButton control
        LinkButton linkButton = new LinkButton();
        linkButton.Text = cellValue;
        
        // Add a JavaScript function to the OnClick attribute of the LinkButton to open the modal popup without a postback
        linkButton.OnClientClick = "showModalPopup('" + cellValue + "'); return false;"; // assuming there is a JavaScript function named 'showModalPopup' that takes the cell value as a parameter

        // Replace the text of the cell with the LinkButton control
        e.Row.Cells[0].Controls.Clear();
        e.Row.Cells[0].Controls.Add(linkButton);
    }
}