Windows Forms FAQ : Windows Forms Form : Syncfusion

32.11 How can I display a form that is 'TopMost' for only my application, but not other applications?

The idea is to create the 'bound' table in your dataset, and then add an extra 'unbound' column. The steps are to derive a custom columnstyle that overrides Paint where you calculate and draw the unbound value. You can also override Edit to prevent the user from selecting your unbound column. Then to get your datagrid to use this special column style, you create a tablestyle and add the column styles to it in the order you want the columns to appear in the datagrid. Here are code snippets that derive the column and use the derived column. You can download a working sample.

// custom column style that is an unbound column

public class DataGridUnboundColumn : DataGridTextBoxColumn

{

protected override void Edit(System.Windows.Forms.CurrencyManager source, int rowNum, System.Drawing.Rectangle bounds, bool readOnly, string instantText, bool cellIsVisible)

{

//do not allow the unbound cell to become active

if(this.MappingName == "UnBound")

return;

base.Edit(source, rowNum, bounds, readOnly, instantText, cellIsVisible);

}

protected override void Paint(System.Drawing.Graphics g, System.Drawing.Rectangle bounds, System.Windows.Forms.CurrencyManager source, int rowNum, System.Drawing.Brush backBrush, System.Drawing.Brush foreBrush, bool alignToRight)

{

//clear the cell

g.FillRectangle(new SolidBrush(Color.White), bounds);

//compute & draw the value

//string s = string.Format("{0} row", rowNum);

// col 0 + 2 chars from col 1

DataGrid parent = this.DataGridTableStyle.DataGrid;

string s = parent[rowNum, 0].ToString() + ((parent[rowNum, 1].ToString())+ " ").Substring(0,2);

Font font = new Font("Arial", 8.25f);

g.DrawString(s, font, new SolidBrush(Color.Black), bounds.X, bounds.Y);

font.Dispose();

}

//code that uses this unbound column

private void Form1_Load(object sender, System.EventArgs e)

{

// Set the connection and sql strings

// assumes your mdb file is in your root

string connString = @"Provider=Microsoft.JET.OLEDB.4.0;data source=C:\northwind.mdb";

string sqlString = "SELECT * FROM customers";

OleDbDataAdapter dataAdapter = null;

DataSet _dataSet = null;

try

{

// Connection object

OleDbConnection connection = new OleDbConnection(connString);

// Create data adapter object

dataAdapter = new OleDbDataAdapter(sqlString, connection);

// Create a dataset object and fill with data using data adapter's Fill method

_dataSet = new DataSet();

dataAdapter.Fill(_dataSet, "customers");

connection.Close();

}

catch(Exception ex)

{

MessageBox.Show("Problem with DB access-\n\n connection: "

+ connString + "\r\n\r\n query: " + sqlString

+ "\r\n\r\n\r\n" + ex.ToString());

this.Close();

return;

}

// Create a table style that will hold the new column style

// that we set and also tie it to our customer's table from our DB

DataGridTableStyle tableStyle = new DataGridTableStyle();

tableStyle.MappingName = "customers";

// since the dataset has things like field name and number of columns,

// we will use those to create new columnstyles for the columns in our DB table

int numCols = _dataSet.Tables["customers"].Columns.Count;

//add an extra column at the end of our customers table

_dataSet.Tables["customers"].Columns.Add("Unbound");

DataGridTextBoxColumn aColumnTextColumn ;

for(int i = 0; i < numCols; ++i)

{

aColumnTextColumn = new DataGridTextBoxColumn();

aColumnTextColumn.HeaderText = _dataSet.Tables["customers"].Columns[i].ColumnName;

aColumnTextColumn.MappingName = _dataSet.Tables["customers"].Columns[i].ColumnName;

tableStyle.GridColumnStyles.Add(aColumnTextColumn);

//display the extra column after column 1.

if( i == 1)

{

DataGridUnboundColumn unboundColStyle = new DataGridUnboundColumn();

unboundColStyle.HeaderText = "UnBound";

unboundColStyle.MappingName = "UnBound";

tableStyle.GridColumnStyles.Add(unboundColStyle); }

}

// make the dataGrid use our new tablestyle and bind it to our table

dataGrid1.TableStyles.Clear();

dataGrid1.TableStyles.Add(tableStyle);

dataGrid1.DataSource = _dataSet.Tables["customers"];

}