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Populate data from database in a ComboBox

By , 19 Oct 2004
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Introduction

This article is the second way (version) of "how to populate data in a ComboBox" program. For doing that, I make use of 'TableMapping' and 'DataViewManager' that I'll explain later in "Code and How it works".

The application allows you to select a StudentID in a ComboBox and displays the columns StudentID, Student Subject and Student Name from the table in the three TextBoxes.

It shows also how to get connected to a MS Access database which you can also find in the project included (sudentDB.mdb). I chose MS Access database because not many people have SQL-Server running.

Form:

Code and How it works

Before starting, a short explanation of what TableMapping and DataViewManager means:

TableMapping is the process that controls how data adapters copy tables and columns of data from a physical data source to ADO.NET in-memory objects. When a data adapter reads data from a data source, it determines where to put the data in the corresponding DataSet table (or tables) using a table mapping. If you create a mapping in a data adapter, it allows you to establish a correspondence between columns in the data source and columns in a DataSet table.

A DataAdapter contains a collection of DataTableMapping objects in its TableMappings property. You can pass the DataTableMapping name in place of the DataTable name to the Fill method of the DataAdapter.

The following example creates a DataTableMapping named "MyStudentMappings" for the table "studentTable".

dAdapter.TableMappings.Add("MyStudentMappings", "studentTable");

When you call the Fill method of the DataAdapter and do not specify a TableName or DataTableMapping name, the DataAdapter looks for a DataTableMapping called "Table". If you leave out that DataTableMapping, TableName of the DataTable will be "Table". This is the default DataTableMapping.

For example:

dAdapter.TableMappings.Add("Table", "studentTable");

If the SELECT command creates a result set with a default name of Table, then its contents go into a new or existing DataTable object called "studentTable". The DataTableMapping object describes a mapped relationship between a SQL-result set and a DataTable object in a DataSet.

The DataViewManager represents a view onto an entire DataSet and represents a databindable, customized view of a DataTable for sorting, filtering, searching, editing, and navigation, whereas the DataView class acts as a view onto a single DataTable.

A DataViewManager is an object that contains a collection of data views. The DataViewManager returned by the DefaultViewManager property allows you to create custom settings for each DataTable in the DataSet. When you want to bind a control to more than one table of a DataSet, binding to a DataViewManager is the ideal choice. When only a single DataTable, then use DataView. When binding a DataSet, .NET automatically uses the corresponding DataViewManager provided through the DataSet.DefaultViewManager property:

For example:

this.dviewmanager=dset.DefaultViewManager;

Here is the code for the method fnGetConnectedToDatabase():

private void fnGetConnectedToDatabase() 
{
  //Connection string
  string conStr = 
    "Provider=Microsoft.Jet.OLEDB.4.0; Data Source=..\\..\\studentDB.mdb";
  try
   {
    //Instantiate OleDbConnection and open the connection to the database
    myConn = new OleDbConnection(conStr);
    myConn.Open();
  }
  catch(OleDbException ex)
  {
    //get the error message if connection failed
    MessageBox.Show("Error in connection ..."+ex.Message);
  }

  string sqlStr ="SELECT * FROM studentTable;";
  //Instantiate a DataAdapter by passing the sqlStr and myConn.
  //now data is in raw form
  dAdapter = new OleDbDataAdapter(sqlStr,myConn);
  //Instantiate a DataSet
  dset = new DataSet();
  //Gets a collection that provides the master mapping
  // between a source table and a DataTable
  dAdapter.TableMappings.Add("Table", "studentTable");

  //A data adapter object utilizes the Fill method to populate 
  //a DataSet or a DataTable object with
  //data retrieved by a SELECT command.
  dAdapter.Fill(dset);
  //When binding a DataSet, .NET automatically uses the corresponding
  //DataViewManager provided through the DataSet.DefaultViewManager property
  this.dviewmanager=dset.DefaultViewManager;
  this.comboBox1.DataSource=this.dviewmanager;
  //display "studentTable.StudentID" in the ComboBox
  this.comboBox1.DisplayMember="studentTable.StudentID";
  //DataBinding for the TextBox controls
  this.textBox1.DataBindings.Add("Text", this.dviewmanager, 
                                         "studentTable.StudentID");
  this.textBox2.DataBindings.Add("Text", this.dviewmanager, 
                                         "studentTable.StudentSubject");
  this.textBox3.DataBindings.Add("Text", this.dviewmanager, 
                                         "studentTable.StudentName");
  // Close the connection to the database.
  this.myConn.Close();
}

As soon as you select a StudentID from the ComboBox, the columns StudentID, StudentSubject and StudentName in the table "studentTable" are displayed in the three TextBoxes.

Conclusion

There are of course many ways to get data into a ComboBox control. I just tried to show a different way.

License

This article has no explicit license attached to it but may contain usage terms in the article text or the download files themselves. If in doubt please contact the author via the discussion board below.

A list of licenses authors might use can be found here

About the Author

Huseyin Altindag
Software Developer (Senior)
United Kingdom United Kingdom
No Biography provided

Comments and Discussions

 
Question[My vote of 2] Good but the sample is incomplete... PinmemberMatjaž Grahek1-Sep-12 0:14 
QuestionHave error message "Child list for field Client_table cannot be created" PinmemberMember 331042518-Aug-12 0:51 
AnswerRe: Have error message "Child list for field Client_table cannot be created" PinmemberHuseyin Altindag19-Aug-12 1:43 
GeneralRe: Have error message "Child list for field Client_table cannot be created" PinmemberMember 331042520-Aug-12 3:21 
Questioniam geeting error on dviewmanager??? Pinmembervinayak chavan12-Jun-12 20:19 
AnswerRe: iam geeting error on dviewmanager??? PinmemberHuseyin Altindag12-Jun-12 23:18 
GeneralRe: iam geeting error on dviewmanager??? Pinmembervinayak chavan12-Jun-12 23:21 
GeneralRe: iam geeting error on dviewmanager??? PinmemberHuseyin Altindag13-Jun-12 0:02 
GeneralRe: iam geeting error on dviewmanager??? Pinmembervinayak chavan13-Jun-12 23:12 
GeneralMy vote of 5 Pinmemberjerry terragnoli3-Dec-10 3:47 
QuestionVisual C# 2008 express edition and SQL Server 2005 Pinmemberaceraspire4736z28-Sep-10 18:40 
AnswerRe: Visual C# 2008 express edition and SQL Server 2005 PinmemberHuseyin Altindag29-Sep-10 10:03 
GeneralCan't update changes to database Pinmemberdragon_n_me2-Jan-09 0:25 
GeneralProblems with populating from combo box! [modified] PinmemberNataliya5-Apr-08 0:13 
GeneralRe: Problems with populating from combo box! PinmemberHuseyin Altindag5-Apr-08 3:27 
GeneralRe: Problems with populating from combo box! PinmemberNataliya5-Apr-08 6:47 
Generalinsert "Select a StudentID" row Pinmember[SK]SpooK12-Mar-08 21:29 
Generalmultiple columns combobox PinmemberAnailizeR5-May-06 2:10 
GeneralComments on Huseyin Altindag article Pinsusspadmavijay31-Jan-05 23:22 
GeneralRe: Comments on Huseyin Altindag article PinmemberHuseyin Altindag5-Feb-05 0:45 

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