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Accepted
Pedro Ávila
Asked: 2020-07-20 17:17:13 +0800 CST 2020-07-20 17:17:13 +0800 CST

ComboBox in DataGridView

  • 772

I work in a Windows Forms app in which I have a DataGridView control in which one of its columns is of type Combobox, I can populate the ComboBox with data without any problem.

The problem I have is that I need the first element that contains the Combobox to be selected, in this case <<Seleccione>>I have not been able to get it at first sight, nothing is seen in the ComboBox until I click to be able to display the ComboBox and be able to select the items .

This way I load the ComboBox

public IEnumerable<UniversalExtend> SelectList(Expression<Func<UnidadMedida, UniversalExtend>> source)
    {
        return _unidadMedidaRepository.SelectList(source);
    }

    public IEnumerable<UniversalExtend> ListaUnidadMedidas
        (Expression<Func<UnidadMedida, UniversalExtend>> source)
    {
        var listaItem = SelectList(source).ToList();
        listaItem.Insert(0, new UniversalExtend() { Id = -1, Descripcion = "<<<Seleccione>>>" });
        return listaItem;
    }

Persistence

public IEnumerable<UniversalExtend> SelectList(Expression<Func<T, UniversalExtend>> source)
    {
        using (var context = new BusinessContext())
        {
            var result = context.Set<T>().AsNoTracking()
                .Select(source).ToList();
            return result;
        }
    }

Binding the data to the ComboBox

dataGridView1.AutoGenerateColumns = false;
        DataGridViewComboBoxColumn cboColMedida = dataGridView1.Columns["colCombo"] as DataGridViewComboBoxColumn;
        cboColMedida.DataSource =
            _saUnidadMedida.ListaUnidadMedidas(
                x => new UniversalExtend() {Id = x.UnidadMedidaId, Descripcion = x.Abreviacion}).ToList();
        cboColMedida.DisplayMember = "Descripcion";
        cboColMedida.ValueMember = "Id";

This is how it is shown when the cbo is already loaded with data. ComboBox

c#

2 Answers

  1. Best Answer

    I've been playing with your code and the answer is quite simple just assign a value to the combobox cell (In your example give it the value -1 that you declared in the Id) right after binding the data with your combobox.

    dataGridView1.Rows[0].Cells["colCombo"].Value =-1;

    In other words, in the part of the code where you assign the DataSource it would look like this:

        dataGridView1.AutoGenerateColumns = false;
    DataGridViewComboBoxColumn cboColMedida = dataGridView1.Columns["colCombo"] as DataGridViewComboBoxColumn;
    cboColMedida.DataSource =
            _saUnidadMedida.ListaUnidadMedidas(
                x => new UniversalExtend() {Id = x.UnidadMedidaId, Descripcion = x.Abreviacion}).ToList();
    cboColMedida.DisplayMember = "Descripcion";
    cboColMedida.ValueMember = "Id";
    dataGridView1.Rows[0].Cells["colCombo"].Value =-1;
    dataGridView1.RowsAdded += DataGridView1OnRowsAdded;

    And the function that will make the selection every time a new row is added would be:

    private void DataGridView1OnRowsAdded(object sender, DataGridViewRowsAddedEventArgs e)
    {
        dataGridView1.Rows[e.RowIndex].Cells["colCombo"].Value = -1;
    }

    I hope you can solve the problem.

    All the best

    • 3

  2. What you need is to capture the default null value of the column in the combobox:

    cboColMedida.DefaultCellStyle.NullValue = "<<<Seleccione>>>";

    This after having finished filling the data to the DataGridViewComboBoxColumn

    • 0