[错误][DataGridView] 索引超出范围

Question

I receive an "Index out of Range" error when I try to change text on Columns Header. See code below:

private void cboMonth_TextChanged(object sender, EventArgs e)
{
    dgvAnnual.DataSource = null;
    dgvAnnual.Rows.Clear();
    dgvAnnual.Columns.Clear();

    BindingSource bSource = new BindingSource();
    bSource.DataSource = ReloadData(dtTable, cboMonth.Text);
    dgvAnnual.DataSource = bSource;

    //Testing Code
    Console.WriteLine(dgvAnnual.Columns.Count); //Col = 4
    Console.WriteLine(dgvAnnual.Rows.Count); //Row = 10

    //The Code below is Working
    string[] str = {"Col1","Col2","Col3","Col4"};
    For(int i = 0;i<dvgAnnual.Columns.Count;i++)
    {
        dvgAnnual.Columns[i].HeaderText = str[i];  //<----- It's ok if it's stay in Loop For, event if I replace i by "0"
    }

    //The Code below not working if it stay outside For
    dgvAnnual.Columns[0].HeaderText = "Col1"; //<----- Error if stay alone like this
}

Answer 1

Working Code :

    private void cboMonth_TextChanged(object sender, EventArgs e)
    {
       dgvAnnual.DataSource = null;
       dgvAnnual.Rows.Clear();
       dgvAnnual.Columns.Clear();

       BindingSource bSource = new BindingSource();
       bSource.DataSource = ReloadData(dtTable, cboMonth.Text);
       dgvAnnual.DataSource = bSource;

       //Using for testing
       Console.WriteLine(dgvAnnual.Columns.Count); //Col = 4
       Console.WriteLine(dgvAnnual.Rows.Count); //Row = 10

       //This Code below Working
       string[] str = {"Col1","Col2","Col3","Col4"};
       For(int i = 0;i<dvgAnnual.Columns.Count;i++)
       {
           dvgAnnual.Columns[i].HeaderText = str[i];  //<----- It's ok if it's stay in Loop For, event if I replace i by "0"
       }
    }

Not Working:

    private void cboMonth_TextChanged(object sender, EventArgs e)
    {
        dgvAnnual.DataSource = null;
        dgvAnnual.Rows.Clear();
        dgvAnnual.Columns.Clear();

        BindingSource bSource = new BindingSource();
        bSource.DataSource = ReloadData(dtTable, cboMonth.Text);
        dgvAnnual.DataSource = bSource;

        //Testing Code
        Console.WriteLine(dgvAnnual.Columns.Count); //Col = 4
        Console.WriteLine(dgvAnnual.Rows.Count); //Row = 10

        //This code below not working
        dgvAnnual.Columns[0].HeaderText = "Col " + 1; //<----- Error: Index out of Range
    }

Error catch on Watch1

    +   dgvAnnual.Columns[0]    'dgvAnnual.Columns[0]' threw an exception of type 'System.ArgumentOutOfRangeException'  System.Windows.Forms.DataGridViewColumn {System.ArgumentOutOfRangeException}

Thanks

Answer 2

The value of the Columns is 4 here but in the loop you have ranged it i = 0; to i<=4 means total number is 5. so change your range of for loop. use i is less then dvgAnnual.Columns.count instead of i is less than and equal to dvgAnnual.Columns.count. Just try it.

    for(int i = 0;i<dvgAnnual.Columns.count;i++)
    {
        dvgAnnual.Columns[i].HeaderText = str[i];  //<----- It's ok if it's stay in Loop For, event if I replace i by "0"
    }      

Answer 3

Solution: the datagridview must be linked to a form

Example: dgv_Example.Parent = frm_Example