C# Winforms how to set Datagridview DataGridViewCheckBoxCell via code

Pat Hanks 141 Reputation points
2023-08-28T18:00:42.5866667+00:00

I am stumped on finding a solution to allow me to set a hidden DataGridViewCheckBoxCell checked state with code. The application is using a DataGridView to present a recipe on the form. Users are allowed to add/change the rows of the recipe. I want to track which rows have been changed to prompt the user for additional actions. I am using the CurrentCellDirtyStateChanged event to capture the change in state. When I try to set the cell to true or false with the following statement, it will cause an exception "Specified cast is not valid.". Note this is only occurring when I am adding a new row to the gridview. If I comment out the line below all rows added to the datagrid are indeed appended to the datatable.

ComponentsDataGridView.CurrentRow.Cells[columnIndex].Value = true

The datagrid is bound to a temp datatable and that column is added as typeof(bool). When the temp table is populated I set the column to false. I have confirmed the value is indeed false after it is populated for all the rows are appended.

In the debugger I confirmed ComponentsDataGridView.CurrentRow.Cells[columnIndex].ValueType returns the value of "Boolean".

As well I confirmed ComponentsDataGridView.CurrentRow.Cells[columnIndex].GetType() returns "System.Windows.Forms.DataGridViewCheckBoxCell" to make sure the index is correct.

The last item I checked is ComponentsDataGridView.CurrentRow.Cells[columnIndex].Value is DBNull returns true.

I have also tried setting ComponentCategoryDirty.TrueValue = true; & ComponentCategoryDirty.FalseValue = false; but it didn't make a difference.

I must be missing something, I just can't seem to find what. Is it possible to set the default state of the DataGridViewCheckBoxCell to false? Am I using the wrong event to set the value in?

Windows Forms
Windows Forms
A set of .NET Framework managed libraries for developing graphical user interfaces.
1,821 questions
C#
C#
An object-oriented and type-safe programming language that has its roots in the C family of languages and includes support for component-oriented programming.
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Accepted answer
  1. Jiale Xue - MSFT 30,811 Reputation points Microsoft Vendor
    2023-08-29T03:06:02.9966667+00:00

    Hi @Pat Hanks , Welcome to Microsoft Q&A,

    Did you forget to set the target column to be the checkbox column?

    I created a BindingList with Boolean properties as a demonstration. Use the AddButton demo to add a row with default false. Use EditButton to demonstrate modifying the boolean property of the target cell.

    using System;
    using System.ComponentModel;
    using System.Windows.Forms;
    
    namespace _8_29_x
    {
        public partial class Form1 : Form
        {
            public Form1()
            {
                InitializeComponent();
            }
    
            public PersonBindingList people = new PersonBindingList();
            private void Form1_Load(object sender, EventArgs e)
            {
                people.Add(new Person(1, "a", true));
                people.Add(new Person(2, "b", false));
                people.Add(new Person(3, "c", true));
                dataGridView1.DataSource = people;
    
            }
    
            private void AddButton_Click(object sender, EventArgs e)
            {
                people.Add(new Person(people.Count + 1, "New Person", false));
            }
    
            private void EditButton_Click(object sender, EventArgs e)
            {
                Boolean adult = (Boolean)dataGridView1.CurrentRow.Cells["adult"].Value;
                dataGridView1.CurrentRow.Cells["adult"].Value = !adult;
            }
        }
        public class Person : INotifyPropertyChanged
        {
            public int Id { get; set; }
            private String _name;
            public String Name
            {
                get { return _name; }
                set
                {
                    _name = value;
                    NotifyPropertyChanged(nameof(Name));
                }
            }
            private Boolean _adult;
            public Boolean Adult
            {
                get { return _adult; }
                set
                {
                    _adult = value;
                    NotifyPropertyChanged(nameof(Adult));
                }
            }
    
            public event PropertyChangedEventHandler PropertyChanged;
            protected void NotifyPropertyChanged(String propertyName)
            {
                PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
            }
    
            public Person(int id, string name, bool adult)
            {
                Id = id;
                Name = name;
                Adult = adult;
            }
        }
    
        public class PersonBindingList : BindingList<Person>
        {
            protected override void OnListChanged(ListChangedEventArgs e)
            {
                if (e.ListChangedType == ListChangedType.ItemAdded)
                {
                    // Automatically add a new row in the DataGridView when a new item is added
                    if (IsSortedCore) // Check if sorting is applied
                    {
                        ApplySortCore(SortPropertyCore, SortDirectionCore); // Reapply sorting to include the new item
                    }
                }
                base.OnListChanged(e);
            }
        }
    }
    

    enter image description here

    Best Regards,

    Jiale


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2 additional answers

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  1. Karen Payne MVP 35,031 Reputation points
    2023-08-29T09:35:17.9566667+00:00

    Since your using a DataTable, to set a default value use DefaultValue as shown here

    DataTable dt = new DataTable();
    dt.Columns.Add(new DataColumn()
    {
        ColumnName = "Checked",
        DataType = typeof(bool),
        DefaultValue = false
    });
    

    In regards to setting an invisible DataGridView column value, you should use a BindingSource, set its source to the DataTable, the BindingSource is now the DataSource of the DataGridView.

    The following shows

    • Defining the DataTable
    • Adding several rows in different styles
    • Setting up the DataGridView (in this case column names are DataColumn names)
    • Toggle the checkbox column value of the current row between true/false
    • Toggle visibility of the checkbox column
    • Raw inspection of checkbox column values
    • Detect new row added, easy to expand on for other actions

    Mocked code

    using System.Data;
    using System.Diagnostics;
    
    #pragma warning disable CS8602 // Dereference of a possibly null reference.
    
    namespace WinFormsApp1;
    
    public partial class Form1 : Form
    {
        private BindingSource _bindingSource = new BindingSource();
        public Form1()
        {
            InitializeComponent();
    
            DataTable dt = new DataTable();
    
            dt.Columns.Add(new DataColumn()
            {
                ColumnName = "Checked",
                DataType = typeof(bool),
                DefaultValue = false
            });
            dt.Columns.Add(new DataColumn()
            {
                ColumnName = "FirstName",
                DataType = typeof(string),
                DefaultValue = ""
            });
            dt.Columns.Add(new DataColumn()
            {
                ColumnName = "LastName",
                DataType = typeof(string),
                DefaultValue = ""
            });
    
            dt.Rows.Add(null, "Karen", "Payne");
            dt.Rows.Add(true, "Mary", "Jones");
    
            DataRow row1 = dt.NewRow();
            row1["FirstName"] = "Bill";
            row1["LastName"] = "Adams";
            dt.Rows.Add(row1);
    
            DataRow row2 = dt.NewRow();
            row2["FirstName"] = "Sue";
            row2["LastName"] = "Gallagher";
            row2["Checked"] = true;
            dt.Rows.Add(row2);
    
            dt.AcceptChanges(); // only for this demo
    
            _bindingSource.DataSource = dt;
            dataGridView1.DataSource = _bindingSource;
            dt.RowChanged += RowChanged;
    
        }
    
        private void ToggleColumnVisibleButton_Click(object sender, EventArgs e)
        {
    
            dataGridView1.Columns["Checked"]!.Visible =
                !dataGridView1.Columns["Checked"]!.Visible;
        }
    
        private void ToggleCheckedButton_Click(object sender, EventArgs e)
        {
            if (_bindingSource.Current is not null)
            {
                DataRow row = ((DataRowView)_bindingSource.Current).Row;
                row.SetField("Checked", 
                    !row.Field<bool>("Checked"));
            }
    
        }
    
        private void InspectButton_Click(object sender, EventArgs e)
        {
            // Get at the DataTable of the BindingSource
            DataTable? table = (DataTable)_bindingSource.DataSource;
    
            var result = table
                .AsEnumerable()
                .Select(row => row.Field<bool>("Checked"))
                .ToList();
    
            foreach (var item in result)
            {
                Debug.WriteLine(item);
            }
    
            Debug.WriteLine("");
        }
    
        public void RowChanged(object sender, DataRowChangeEventArgs e)
        {
            if (e.Action != DataRowAction.Add) return;
            DataRow row = e.Row;
            // apostrophes are there in the event there is no value for first or last name
            Debug.WriteLine($"{row["Checked"]}  '{row["FirstName"]}'  '{row["LastName"]}'");
        }
    
        private void GetModificationsButton_Click(object sender, EventArgs e)
        {
            DataTable? table = (DataTable)_bindingSource.DataSource;
            DataTable? changedTable = table.GetChanges(DataRowState.Modified);
            if (changedTable is not null)
            {
                // there are changes, inspect the row(s) and column(s)
            }
            else
            {
                // no changes
            }
        }
    }
    

  2. Pat Hanks 141 Reputation points
    2023-08-31T19:04:07.4633333+00:00

    I want to thank you guys for the great suggestions and knowledge. After being able to get some uninterrupted head-down time on this I was able to find a solution and what I believe was the cause of my problem. Since I was using the CurrentCellDirtyStateChanged event, at this point there is no underlying datarow of the grid row to modify yet. I checked the row count of the ComponentDataView.Table. That I believe explains why I was getting a DBNull in the checkbox value, which was generating the invalid cast exception.

    Once I changed my approach to create a class object with properties that match by checkboxes I was able to set them to true/false in the CurrentCellDirtyStateChanged event.

    private partial class GridRowDirtyFlags
    {    
    	public bool Qty { get;set; }    
    	public bool Category { get; set; }    
    	public bool Item { get; set; }    
    	public bool UOM { get; set; }    
    	public void SetFlags(bool State)    
    	{        
    		Qty = State;        
    		Category = State;        
    		Item = State;        
    		UOM = State;    
    	}
    }
    
    

    Then in the RowValidating event, I am able to update the checkbox values without incident.

    I welcome any feedback on my approach.

    DataGridViewRow row = ComponentsDataGridView.Rows[e.RowIndex];	
    row.Cells[ComponentCategoryDirty.Index].Value = _gridRowDirtyFlags.Category;
    row.Cells[ComponentItemDirty.Index].Value = _gridRowDirtyFlags.Item;
    row.Cells[ComponentQtyDirty.Index].Value = _gridRowDirtyFlags.Qty;
    row.Cells[ComponentUOMDirty.Index].Value = _gridRowDirtyFlags.UOM;
    // reset the flags
    _gridRowDirtyFlags.SetFlags(false);