以编程方式将新列添加到DataGridView

Question

I have a DataGridView bound to a DataTable. The DataTable is populated from a database query. The table contains a column named BestBefore. BestBefore is a date formatted as a string (SQLite doesn't have date types).

I would like to programmatically add a new column to the DataGridView called Status. If BestBefore is less than the current date, Status value should be set to OK, otherwise Status value should be set to NOT OK.

I'm very new to Winforms, so some example code would be greatly appreciated.

UPDATE:

I think DataColumn.Expression is okay for doing simple calculations such multiplying a column's integer value by another value, but what about doing what I need to do? That is, calculate the difference between now and the date (string formatted) in the BestBefore column to determine what value to give the new status column. Example code would be appreciated.

Answer 1

Keep it simple

dataGridView1.Columns.Add("newColumnName", "Column Name in Text");

To add rows

dataGridView1.Rows.Add("Value for column#1"); // [,"column 2",...]

Answer 2

Add new column to DataTable and use column Expression property to set your Status expression.

Here you can find good example: DataColumn.Expression Property

DataTable and DataColumn Expressions in ADO.NET - Calculated Columns

UPDATE

Code sample:

DataTable dt = new DataTable();
dt.Columns.Add(new DataColumn("colBestBefore", typeof(DateTime)));
dt.Columns.Add(new DataColumn("colStatus", typeof(string)));

dt.Columns["colStatus"].Expression = String.Format("IIF(colBestBefore < #{0}#, 'Ok','Not ok')", DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss"));

dt.Rows.Add(DateTime.Now.AddDays(-1));
dt.Rows.Add(DateTime.Now.AddDays(1));
dt.Rows.Add(DateTime.Now.AddDays(2));
dt.Rows.Add(DateTime.Now.AddDays(-2));

demoGridView.DataSource = dt;

UPDATE #2

dt.Columns["colStatus"].Expression = String.Format("IIF(CONVERT(colBestBefore, 'System.DateTime') < #{0}#, 'Ok','Not ok')", DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss"));

Answer 3

Here's a sample method that adds two extra columns programmatically to the grid view:

    private void AddColumnsProgrammatically()
    {
        // I created these columns at function scope but if you want to access 
        // easily from other parts of your class, just move them to class scope.
        // E.g. Declare them outside of the function...
        var col3 = new DataGridViewTextBoxColumn();
        var col4 = new DataGridViewCheckBoxColumn();

        col3.HeaderText = "Column3";
        col3.Name = "Column3";

        col4.HeaderText = "Column4";
        col4.Name = "Column4";

        dataGridView1.Columns.AddRange(new DataGridViewColumn[] {col3,col4});
    }

A great way to figure out how to do this kind of process is to create a form, add a grid view control and add some columns. (This process will actually work for ANY kind of form control. All instantiation and initialization happens in the Designer.) Then examine the form's Designer.cs file to see how the construction takes place. (Visual Studio does everything programmatically but hides it in the Form Designer.)

For this example I created two columns for the view named Column1 and Column2 and then searched Form1.Designer.cs for Column1 to see everywhere it was referenced. The following information is what I gleaned and, copied and modified to create two more columns dynamically:

// Note that this info scattered throughout the designer but can easily collected.

        System.Windows.Forms.DataGridViewTextBoxColumn Column1;
        System.Windows.Forms.DataGridViewCheckBoxColumn Column2;

        this.Column1 = new System.Windows.Forms.DataGridViewTextBoxColumn();
        this.Column2 = new System.Windows.Forms.DataGridViewCheckBoxColumn();

        this.dataGridView1.Columns.AddRange(new System.Windows.Forms.DataGridViewColumn[] {
        this.Column1,
        this.Column2});

        this.Column1.HeaderText = "Column1";
        this.Column1.Name = "Column1";

        this.Column2.HeaderText = "Column2";
        this.Column2.Name = "Column2";