Unable to cast object of type 'System.Windows.Controls.DataGridTextColumn' to type 'System.IConvertible' error

Question

I am building a WPF form with a datagrid that pulls the data from the datagrid when a checkbox is checked to "select" that row.

DOC_Number is an int but it's pulled data in the datagrid from a SQL server. I have tried to convert it to a string or to text because it was telling me that it was unacceptable as an integer prior, now it won't convert to a string.

I'm unsure if it's not getting the checkbox data properly or if DOC_Number is not registering as an int.

I'm getting an error:

System.InvalidCastException: 'Unable to cast object of type 'System.Windows.Controls.DataGridTextColumn' to type 'System.IConvertible'

at the line int DocIdx = Convert.ToInt32(DOC_Number);

private void BtnGridUpdate_Click(object sender, EventArgs e)
{
    int employeeID = Convert.ToInt32(EmpID.Text);
    UpdateInternal0(employeeID);
} 

void UpdateInternal0(int employeeId)
{
    try
    {
        using (SqlConnection con = new SqlConnection(Properties.Settings.Default.adminConnectionString))
        {
            con.Open();

            foreach (DataRowView drv in InternalGrid0.SelectedItems)
            {
                DataRow row = drv.Row;
                bool isSelected = Convert.ToBoolean(drv.Row[0]);
                if (isSelected)
                {
                    string sqlString = "INSERT INTO ChecklistTransitionTable (RelatedEmployeeID, RelatedDocIdx) VALUES (@EmpID, @DOC_Number)";

                    using (SqlCommand cmd = new SqlCommand(sqlString, con))
                    {
                        for (int i = 0; i < InternalGrid0.Columns.Count; i++) 
                        {

                            int DocIdx = Convert.ToInt32(DOC_Number);
                            int employeeID = Convert.ToInt32(EmpID.Text);

                            cmd.Parameters.AddWithValue("@EmpID", employeeID = (int)row[i]);
                            cmd.Parameters.AddWithValue("@DOC_Number", DocIdx = (int)row[i]);

                            int result = cmd.ExecuteNonQuery();
                            cmd.Parameters.Clear();

                            Console.WriteLine("Test");
                            //Check Error
                            if (result < 0)
                            {
                                System.Windows.Forms.MessageBox.Show("Error inserting data into database!");
                            }
                        }
                    }
                }
            }
        }

        System.Windows.Forms.MessageBox.Show("Employee data successfully updated.");
    }

    catch (SqlException ex)
    {
        System.Windows.Forms.MessageBox.Show(string.Format("\nMessage ---\n{0}", ex.Message));
    }
}

Answer 1

for loop over columns doesn't make sense. you should be able to get document id from DataRow row object:

foreach (DataRowView drv in InternalGrid0.SelectedItems)
{
    DataRow row = drv.Row;
    bool isSelected = Convert.ToBoolean(drv.Row[0]);
    if (isSelected)
    {
        string sqlString = "INSERT INTO ChecklistTransitionTable (RelatedEmployeeID, RelatedDocIdx) VALUES (@EmpID, @DOC_Number)";

        using (SqlCommand cmd = new SqlCommand(sqlString, con))
        {
            int DocIdx = Convert.ToInt32(row["DOC_Number"]);

            cmd.Parameters.AddWithValue("@EmpID", employeeId);
            cmd.Parameters.AddWithValue("@DOC_Number", DocIdx);

            int result = cmd.ExecuteNonQuery();
            if (result < 0)
            {
                System.Windows.Forms.MessageBox.Show("Error inserting data into database!");
            }
        }
    }
}