How to Get Value Member in a ComboBox Using C# and SQL Server

How to Get Value Member in a ComboBox Using C# and SQL Server

Now, in this tutorial, I will show you how to get the value member in a ComboBox by using C# and SQL Server. This method is very important in selecting the exact data that has been listed in the ComboBox. For example, when you want to display the list of books in the ComboBox that came from the database but you only want to get its id. That’s where you use the value member to get the id of a book that is listed in the ComboBox.

Database : Click here for the database of this project.

Let’s begin:

Open Microsoft Visual Studio and create a new windows application for C#. Then, do the form just like this.

After setting up the form, go to the solution explorer and hit “code view” to fire the code editor.

In the code editor, declare all the classes and variable that are needed.

Note: Put “using System.Data.SqlClient;” above the namespace to access sql server library.

 //initializes new instance 
 SqlConnection con = new SqlConnection();
 SqlDataAdapter da = new SqlDataAdapter();
 SqlCommand cmd = new SqlCommand();
 DataTable dt = new DataTable();
 //declare a variable
 string query;

After that, create a method for filling data in the list control of a ComboBox.

 //a method for filling data in the combobox
 private void LoadBooks(string query, ComboBox cbo)
 {
 //opening connection
 con.Open();
 try
 {
 //initialize a new instance of sqlcommand
 cmd = new SqlCommand();
 //set a connection used by this instance of sqlcommand
 cmd.Connection = con;
 //set the sql statement to execute at the data source
 cmd.CommandText = query;
 //initialize a new instance of sqlDataAdapter
 da = new SqlDataAdapter();
 //set the sql statement or stored procedure to execute at the data source
 da.SelectCommand = cmd;
 //initialize a new instance of DataTable
 dt = new DataTable();
 //add or resfresh rows in the certain range in the datatable to match those in the data source.
 da.Fill(dt);

 //Get and set the data source of a comboBox
 cbo.DataSource = dt;
 //set the field of a table to display in the list control of a combo box
 cbo.DisplayMember = "BooksName";
 //'SET THE ACTUAL VALUE OF THE 
 //' ITEMS IN THE COMBOBOX
 cbo.ValueMember = "ID";
 //Display first in the list control
 cbo.Text = "Select";

 }
 catch (Exception ex)
 {
 //catching error 
 MessageBox.Show(ex.Message);
 }
 //release all resources used by the component
 da.Dispose();
 //closing connection
 con.Close();
 }

Go back to the design view, double-click the form and do the following codes to establish the connection between SQL Server 2005 Express Edition and C#.net.

 //set a connection between SQL server and Visual C#
 con.ConnectionString = "Data Source=.\\SQLEXPRESS;Database=dbbooks;trusted_connection=true;";
 //set up a retrieve query
 query = "Select * From tblbooks";
 LoadBooks(query, comboBox1 );//call a load method

Go back to the design view again, double-click a ComboBox and do the following codes for getting the value member of a ComboBox when selected.

 MessageBox.Show("Book Id : " + comboBox1.SelectedValue.ToString());

Output:

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