Maintain (Keep selected) checked CheckBoxes in GridView when adding new row using C# in ASP.Net

Hi ,

Refer the below sample code for your reference.

As its CheckBoxList You always need to loop for selected item to store value of selected items also you need to check value by using FindByValue for each selected itemvalue and need to set it as selected true.

C#

private void SetPreviousDataLecturer()
{
int rowIndex = 0;
if (ViewState["LecturerGridView"] != null)
{
    DataTable dataTableCurrent = (DataTable)ViewState["LecturerGridView"];
    if (dataTableCurrent.Rows.Count > 0)
    {
        for (int i = 0; i < dataTableCurrent.Rows.Count; i++)
        {
            TextBox textBoxLName = (TextBox)LecturerGridView.Rows[rowIndex].Cells[1].FindControl("LecturerName");
            TextBox textBoxLID = (TextBox)LecturerGridView.Rows[rowIndex].Cells[2].FindControl("LecturerID");
            TextBox textBoxLAdd = (TextBox)LecturerGridView.Rows[rowIndex].Cells[3].FindControl("LecturerAddress");
            TextBox textBoxLPNumber = (TextBox)LecturerGridView.Rows[rowIndex].Cells[4].FindControl("LecturerPNumber");
            TextBox textBoxLEAdd = (TextBox)LecturerGridView.Rows[rowIndex].Cells[5].FindControl("LecturerEAddress");
            CheckBoxList checkBoxListLCourse = (CheckBoxList)LecturerGridView.Rows[rowIndex].Cells[6].FindControl("LecturerCourse");
            TextBox textBoxLPassword = (TextBox)LecturerGridView.Rows[rowIndex].Cells[7].FindControl("LecturerPassword");

            LecturerGridView.Rows[i].Cells[0].Text = Convert.ToString(i + 1);
            textBoxLName.Text = dataTableCurrent.Rows[i]["LecturerName"].ToString();
            textBoxLID.Text = dataTableCurrent.Rows[i]["LecturerID"].ToString();
            textBoxLAdd.Text = dataTableCurrent.Rows[i]["LecturerAddress"].ToString();
            textBoxLPNumber.Text = dataTableCurrent.Rows[i]["LecturerPNumber"].ToString();
            textBoxLEAdd.Text = dataTableCurrent.Rows[i]["LecturerEAddress"].ToString();

            string lecturerCourse = dataTableCurrent.Rows[i]["LecturerCourse"].ToString();
            if (!string.IsNullOrEmpty(lecturerCourse))
            {
                for (int j = 0; j < lecturerCourse.Split(',').Length; j++)
                {
                    checkBoxListLCourse.Items.FindByValue(lecturerCourse.Split(',')[j].ToString()).Selected = true;
                }
            }                    
            textBoxLPassword.Text = dataTableCurrent.Rows[i]["LecturerPassword"].ToString();
            rowIndex++;
        }
    }
}
}

private void AddNewRowToLecturerGV()
{
int rowIndex = 0;
if (ViewState["LecturerGridView"] != null)
{
    DataTable dataTableCurrent = (DataTable)ViewState["LecturerGridView"];
    DataRow dataRowCurrent = null;
    if (dataTableCurrent.Rows.Count > 0)
    {
        for (int i = 1; i <= dataTableCurrent.Rows.Count; i++)
        {
            TextBox textBoxLName = (TextBox)LecturerGridView.Rows[rowIndex].Cells[1].FindControl("LecturerName");
            TextBox textBoxLID = (TextBox)LecturerGridView.Rows[rowIndex].Cells[2].FindControl("LecturerID");
            TextBox textBoxLAdd = (TextBox)LecturerGridView.Rows[rowIndex].Cells[3].FindControl("LecturerAddress");
            TextBox textBoxLPNumber = (TextBox)LecturerGridView.Rows[rowIndex].Cells[4].FindControl("LecturerPNumber");
            TextBox textBoxLEAdd = (TextBox)LecturerGridView.Rows[rowIndex].Cells[5].FindControl("LecturerEAddress");
            CheckBoxList checkBoxListLCourse = (CheckBoxList)LecturerGridView.Rows[rowIndex].Cells[6].FindControl("LecturerCourse");
            TextBox textBoxLPassword = (TextBox)LecturerGridView.Rows[rowIndex].Cells[7].FindControl("LecturerPassword");

            dataRowCurrent = dataTableCurrent.NewRow();
            dataRowCurrent["RowNumber"] = i + 1;
            dataTableCurrent.Rows[i - 1]["LecturerName"] = textBoxLName.Text;
            dataTableCurrent.Rows[i - 1]["LecturerID"] = textBoxLID.Text;
            dataTableCurrent.Rows[i - 1]["LecturerAddress"] = textBoxLAdd.Text;
            dataTableCurrent.Rows[i - 1]["LecturerPNumber"] = textBoxLPNumber.Text;
            dataTableCurrent.Rows[i - 1]["LecturerEAddress"] = textBoxLEAdd.Text;

            string lecturerCourse = string.Empty;
            foreach (ListItem item in checkBoxListLCourse.Items)
            {
                if (item.Selected)
                {
                    if (!string.IsNullOrEmpty(lecturerCourse))
                    {
                        lecturerCourse += ",";
                    }
                    lecturerCourse += item.Value;
                }
            }

            dataTableCurrent.Rows[i - 1]["LecturerCourse"] = lecturerCourse;
            dataTableCurrent.Rows[i - 1]["LecturerPassword"] = textBoxLPassword.Text;

            rowIndex++;
        }

        dataTableCurrent.Rows.Add(dataRowCurrent);
        ViewState["LecturerGridView"] = dataTableCurrent;

        LecturerGridView.DataSource = dataTableCurrent;
        LecturerGridView.DataBind();
    }
}
else
{
    Response.Write("ViewState is null.");
}
SetPreviousDataLecturer();
}