Dynamic Control Validation at Runtime using a Container Control

• Download source code - 339.0 Kb

Introduction

Child controls (textbox, combo etc.) in a .NET container controls (like a Form), can be accessed and their properties set at runtime dynamically by accessing the control array.

Using the Code

The following example deals with runtime validation (which checks for compulsory data input) of Windows Forms controls like TextBox, RichTextBox and ComboBox but can be expanded to handle validation and appearance of all types of Windows Forms controls.

To implement this example, you must create a database table which would hold the configuration for all the controls in the forms. You can also use an XML file instead of a database table.

I have attached the SQL to create the MS SQL 2000 database as well as the database backup. You have to create and configure the database at your end. After you restore the database, you will see that the table 'Ctlvalidation' has the form name, the control name, message and compulsory flag fields.

ID	Form	CtlName	Msg	Compulsory
1	Form1	textBox1	Name	0
2	Form1	comboBox1	Age	1
3	Form1	richTextBox1	Comments	0

Our application will read this table and depending upon the flag set in the Compulsory field, will make the control compulsory or non compulsory.

In our application, we create the CompulsoryLogic class, which we can then call from any form in the application. In this class, we first create a database connection and fill the DataSet ds.

string source = "server=CHAYAN;uid=mine;pwd=mine;database=CtlValidation";
string select = 
   "Select CtlName,Msg from CtlValidation where Compulsory>0 and Form ='"+
   frm.Name.ToString()+"'";
SqlConnection conn = new SqlConnection(source);
SqlDataAdapter da = new SqlDataAdapter(select,conn);
DataSet ds = new DataSet();
da.Fill(ds,"CtlValidation");

Then we loop through each DataRow in the DataSet and for each control in the form, check the validation for the required control (textbox, rich textbox or combo).

foreach(DataRow dr in ds.Tables[0].Rows)
{
  foreach (Control c in frm.Controls)
  {
    if (c.Name == dr[0].ToString())
    { 
      //check to see if the control is of type textbox or a richtextbox
      if (c.GetType().ToString().EndsWith("TextBox"))
      {
        //check to see if the box is empty
        if (c.Text =="")
        {
          MessageBox.Show(dr[1].ToString()+" is a compulsory field",
               "Compulsory Field",0);
          c.BackColor = Color.AliceBlue;
          c.Focus();
        }
      }
    //check to see if the control is of type combo
    // More code here
  }
}

Once this is done, we can call the CompulsoryLogic class from any form where a control validation is required.

private void button1_Click(object sender, EventArgs e)
{

  CompulsoryLogic.ValidateCtl(this);

}

A very similar concept can be used in providing menu based security to user groups in a desktop application but we will discuss that in a separate article.

Prerequisites

1. MS SQL 2000
2. VS.NET 2003 (C#)