how to read a all rows in a specific column and change before binding in grid view asp.net

Question

I have a SQL Table where it contains one column all hexabinary values. While retrieving the data from the table in a grid view.I need to change all its value in a particular column with and then binding.

foreach (DataRow dr in ds.Tables[0].Rows)
        {
            for (int i = 0; i < ds.Tables[0].Rows.Count; i++)
            {
                object o = dr["ColumnName"];
                if (o != DBNull.Value) // Check for null
                {

                    if (ds.Tables[0].Rows[i]["ColumnName"].ToString() != null)
                    {
                        ds.Tables[0].Rows[i]["ColumnName"] = value.ToString();
                    }
                    else
                    { }
                }
            }
        }
ds.Tables[0].AcceptChanges();
grid.DataSource = ds;
grid.DataBind();

I am trying to loop through only one particular column and change all the values in that. But it is failing. please help me

Answer 1

Since ds.Tables[0] contains DataTable object, you can use DataRow.Field<T>() extension method to find values from specified column name, replace the values with SetField() and then rebind changes to grid's data source:

foreach (DataRow dr in ds.Tables[0].Rows)
{
    string oldValue = dr.Field<string>("ColumnName");

    // check if the column has value
    if (!string.IsNullOrEmpty(oldValue))
    {
        dr.SetField("ColumnName", value.ToString());
    }
    else
    {
        // do something else
    }
}

ds.Tables[0].AcceptChanges();

// rebind the data source here

Note that DataRow.Field<T> casts the value to type specified by T type parameter, hence the following if-condition uses check against null or empty string instead of DBNull.Value .

Answer 2

first, bind your grid view and add OnRowDataBound like

<asp:GridView ID="GridView1" runat="server" OnRowDataBound = "OnRowDataBound">

RowDataBound event is triggered for each GridView Row when the GridView Row is bound to data. then in your on OnRowDataBound event code

protected void OnRowDataBound(object sender, GridViewRowEventArgs e)
{
    if (e.Row.RowType == DataControlRowType.DataRow)
    {
        column1 = e.Row.Cells[1].Text;
        //here you can give the column no that you want get like e.Row.Cells[1] 
        e.Row.Cells[1].Text="test";
       //you can set what you want like this
    }
}