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FormParameter.FormField Property

Note: This property is new in the .NET Framework version 2.0.

Gets or sets the name of the form variable that the parameter binds to.

Namespace: System.Web.UI.WebControls
Assembly: System.Web (in system.web.dll)

public string FormField { get; set; }
/** @property */
public String get_FormField ()

/** @property */
public void set_FormField (String value)

public function get FormField () : String

public function set FormField (value : String)

Property Value

A string that identifies the form variable that the parameter binds to.

The FormField identifies a name/value pair that is passed in the Form collection. While the FormField property identifies the name of the pair, the FormParameter binds to its corresponding value at run time. If the expected form variable string name/value pair is not passed to the Web Forms page in the collection, the Evaluate method binds the parameter to the value of the DefaultValue property, if it is set. If the DefaultValue is not set, the Evaluate method fails to bind the parameter to a value.

The following code example demonstrates how to display filtered data using an ObjectDataSource control and a FormParameter to retrieve data from a middle-tier business object and a GridView control to display the results.

The code example consists of a TextBox, a GridView control, the ObjectDataSource control, and a submit button. By default, the TextBox is populated with the name of one of the Northwind Traders employees. The GridView displays information about the employee identified by the name in the TextBox. To retrieve data on another employee, enter the full name of the employee in the TextBox and click the button.

The FilterExpression property specifies an expression used to filter the data retrieved by the SelectMethod. This property uses parameter placeholders that are evaluated to the parameters contained in the FilterParameters collection. In this example, the parameter placeholder is a FormParameter bound to the value of the TextBox control.

<%@ Register TagPrefix="aspSample" Namespace="Samples.AspNet.CS" Assembly="Samples.AspNet.CS" %>
<%@ Page language="c#" %>
<script runat="server">

    protected void ObjectDataSource1_Filtering(object sender, ObjectDataSourceFilteringEventArgs e)
    {
        if (Textbox1.Text == "")
        {
            e.ParameterValues.Clear();
            e.ParameterValues.Add("FullName", "Nancy Davolio");
        }
    }
</script>

<html>
  <head>
    <title>ObjectDataSource - C# Example</title>
  </head>
  <body>
    <form id="Form1" method="post" runat="server">

        <p>Show all users with the following name.</p>

        <asp:textbox id="Textbox1" runat="server" text="Nancy Davolio" />

        <asp:gridview
          id="GridView1"
          runat="server"
          datasourceid="ObjectDataSource1"
          autogeneratecolumns="False">
          <columns>
            <asp:boundfield headertext="ID" datafield="EmpID" />
            <asp:boundfield headertext="Name" datafield="FullName" />
            <asp:boundfield headertext="Street Address" datafield="Address" />
          </columns>
        </asp:gridview>

        <!-- Security Note: The ObjectDataSource uses a FormParameter,
             Security Note: which does not perform validation of input from the client. -->

        <asp:objectdatasource
          id="ObjectDataSource1"
          runat="server"
          selectmethod="GetAllEmployeesAsDataSet"
          typename="Samples.AspNet.CS.EmployeeLogic"
          filterexpression="FullName='{0}'" OnFiltering="ObjectDataSource1_Filtering">
            <filterparameters>
              <asp:formparameter name="FullName" formfield="Textbox1" defaultvalue="Nancy Davolio" />
            </filterparameters>
        </asp:objectdatasource>

        <p><asp:button id="Button1" runat="server" text="Search" /></p>

    </form>
  </body>
</html>

<%@ Register TagPrefix="aspSample" Namespace="Samples.AspNet.JSL" Assembly="Samples.AspNet.JSL" %>
<%@ Page language="VJ#" %>
<script runat="server">

    protected void ObjectDataSource1_Filtering(Object sender, ObjectDataSourceFilteringEventArgs e)
    {
        if (Textbox1.get_Text() == "")
        {
            e.get_ParameterValues().Clear();
            e.get_ParameterValues().Add("FullName", "Nancy Davolio");
        }
    }
</script>

<html>
  <head>
    <title>ObjectDataSource - VJ# Example</title>
  </head>
  <body>
    <form id="Form1" method="post" runat="server">

        <p>Show all users with the following name.</p>

        <asp:textbox id="Textbox1" runat="server" text="Nancy Davolio" />

        <asp:gridview
          id="GridView1"
          runat="server"
          datasourceid="ObjectDataSource1"
          autogeneratecolumns="False">
          <columns>
            <asp:boundfield headertext="ID" datafield="EmpID" />
            <asp:boundfield headertext="Name" datafield="FullName" />
            <asp:boundfield headertext="Street Address" datafield="Address" />
          </columns>
        </asp:gridview>

        <asp:objectdatasource
          id="ObjectDataSource1"
          runat="server"
          selectmethod="GetAllEmployeesAsDataSet"
          typename="Samples.AspNet.JSL.EmployeeLogic"
          filterexpression="FullName='{0}'" OnFiltering="ObjectDataSource1_Filtering">
            <filterparameters>
              <asp:formparameter name="FullName" formfield="Textbox1" defaultvalue="Nancy Davolio" />
            </filterparameters>
        </asp:objectdatasource>

        <p><asp:button id="Button1" runat="server" text="Search" /></p>

    </form>
  </body>
</html>

The following code example shows the middle-tier business object that the previous code example uses. This example consists of two basic classes: The EmployeeLogic class encapsulates business logic, and the NorthwindEmployee class is a model class that contains only the basic functionality required to load and persist data from the data tier. For simplicity, the EmployeeLogic class creates a static set of data, rather than retrieving the data from a data tier. It is also helpful for this example, because the sample relies on the user to provide the full name of a Northwind Traders employee to demonstrate filtering. For a complete working example, you must compile and use these classes with the Web Forms code examples provided.

namespace Samples.AspNet.CS {

using System;
using System.Collections;
using System.Data;
using System.Web.UI.WebControls;
  //
  // EmployeeLogic is a stateless business object that encapsulates 
  // the operations you can perform on a NorthwindEmployee object.
  //
  public class EmployeeLogic {
  
    
    // Returns a collection of NorthwindEmployee objects.
    public static ICollection GetAllEmployees () {
      ArrayList data = new ArrayList();
           
      data.Add(new NorthwindEmployee(1,"Nancy","Davolio","507 - 20th Ave. E. Apt. 2A"));
      data.Add(new NorthwindEmployee(2,"Andrew","Fuller","908 W. Capital Way"));
      data.Add(new NorthwindEmployee(3,"Janet","Leverling","722 Moss Bay Blvd."));
      data.Add(new NorthwindEmployee(4,"Margaret","Peacock","4110 Old Redmond Rd."));
      data.Add(new NorthwindEmployee(5,"Steven","Buchanan","14 Garrett Hill"));
      data.Add(new NorthwindEmployee(6,"Michael","Suyama","Coventry House Miner Rd."));
      data.Add(new NorthwindEmployee(7,"Robert","King","Edgeham Hollow Winchester Way"));
      
      return data;
    }
    
    public static NorthwindEmployee GetEmployee(object anID) {
      ArrayList data = GetAllEmployees() as ArrayList;     
      int empID = Int32.Parse(anID.ToString());      
      return data[empID] as NorthwindEmployee;
    }

    // 
    // To support basic filtering, the employees cannot
    // be returned as an array of objects, rather as a 
    // DataSet of the raw data values. 
    public static DataSet GetAllEmployeesAsDataSet () {
      ICollection employees = GetAllEmployees();
      
      DataSet ds = new DataSet("Table");
      
      // Create the schema of the DataTable.
      DataTable dt = new DataTable();
      DataColumn dc;
      dc = new DataColumn("EmpID",   typeof(int));    dt.Columns.Add(dc);
      dc = new DataColumn("FullName",typeof(string)); dt.Columns.Add(dc);
      dc = new DataColumn("Address", typeof(string)); dt.Columns.Add(dc);
      
      // Add rows to the DataTable.
      DataRow row;
            
      foreach (NorthwindEmployee ne in employees) {                
        row = dt.NewRow();
        row["EmpID"]    = ne.EmpID;
        row["FullName"] = ne.FullName;
        row["Address"]  = ne.Address;
        dt.Rows.Add(row);
      } 
      // Add the complete DataTable to the DataSet.
      ds.Tables.Add(dt);
      
      return ds;
    }    
  }

  public class NorthwindEmployee {

    public NorthwindEmployee (int anID, 
                              string aFirstName,
                              string aLastName,
                              string anAddress) {
      ID = anID;
      firstName = aFirstName;
      lastName = aLastName;   
      address = anAddress;
    }

    private object ID;
    public string EmpID {
      get { return ID.ToString();  }
    }

    private string lastName;
    public string LastName {
      get { return lastName; }
      set { lastName = value; }
    }

    private string firstName;
    public string FirstName {
      get { return firstName; }
      set { firstName = value;  }
    }
    
    public string FullName {
      get { return FirstName  + " " +  LastName; }
    }
    
    private string address;
    public string Address {
      get { return address; }
      set { address = value;  }
    }    
    
  }
}

package Samples.AspNet.JSL ; 
import System .* ;
import System.Collections .* ;
import System.Data .* ;
import System.Web.UI.WebControls .* ;
//
// EmployeeLogic is a stateless business object that encapsulates 
// the operations you can perform on a NorthwindEmployee object.
//
public class EmployeeLogic
{
    // Returns a collection of NorthwindEmployee objects.
    public static ICollection GetAllEmployees()
    {
        ArrayList data = new ArrayList();

        data.Add(new NorthwindEmployee(1, "Nancy", "Davolio", 
            "507 - 20th Ave. E. Apt. 2A"));
        data.Add(new NorthwindEmployee(2, "Andrew", "Fuller", 
            "908 W. Capital Way"));
        data.Add(new NorthwindEmployee(3, "Janet", "Leverling", 
            "722 Moss Bay Blvd."));
        data.Add(new NorthwindEmployee(4, "Margaret", "Peacock", 
            "4110 Old Redmond Rd."));
        data.Add(new NorthwindEmployee(5, "Steven", "Buchanan", 
            "14 Garrett Hill"));
        data.Add(new NorthwindEmployee(6, "Michael", "Suyama", 
            "Coventry House Miner Rd."));
        data.Add(new NorthwindEmployee(7, "Robert", "King", 
            "Edgeham Hollow Winchester Way"));
        return data;
    } //GetAllEmployees


    public static NorthwindEmployee GetEmployee(Object anID)
    {
        ArrayList data = (ArrayList)GetAllEmployees();
        int empID = Int32.Parse(String.valueOf(anID));

        return (NorthwindEmployee)data.get_Item(empID);
    } //GetEmployee


    // 
    // To support basic filtering, the employees cannot
    // be returned as an array of objects, rather as a 
    // DataSet of the raw data values. 
    public static DataSet GetAllEmployeesAsDataSet()
    {
        ICollection employees = GetAllEmployees();
        DataSet ds = new DataSet("Table");

        // Create the schema of the DataTable.
        DataTable dt = new DataTable();
        DataColumn dc;

        dc = new DataColumn("EmpID", int.class.ToType());
        dt.get_Columns().Add(dc);
        dc = new DataColumn("FullName", String.class.ToType());
        dt.get_Columns().Add(dc);
        dc = new DataColumn("Address", String.class.ToType());
        dt.get_Columns().Add(dc);

        // Add rows to the DataTable.
        DataRow row;

		IEnumerator iterator = employees.GetEnumerator();
        for (int iCtr = 0; iCtr < employees.get_Count(); iCtr++) {
			iterator.MoveNext();
            NorthwindEmployee ne = 
                (NorthwindEmployee)iterator.get_Current();

            row = dt.NewRow();
            row.set_Item("EmpID", ne.get_EmpID());
            row.set_Item("FullName", ne.get_FullName());
            row.set_Item("Address", ne.get_Address());
            dt.get_Rows().Add(row);
        }

        // Add the complete DataTable to the DataSet.
        ds.get_Tables().Add(dt);
        return ds;
    } //GetAllEmployeesAsDataSet
} //EmployeeLogic



public class NorthwindEmployee
{
    public NorthwindEmployee(int anID, String aFirstName, String aLastName, 
        String anAddress)
    {
        ID = new Integer(anID);
        firstName = aFirstName;
        lastName = aLastName;
        address = anAddress;
    } //NorthwindEmployee


    private Object ID;


    /** @property */
    public String get_EmpID()
    {
        return ID.toString();
    } //get_EmpID


    private String lastName;


    /** @property */
    public String get_LastName()
    {
        return lastName;
    } //get_LastName


    /** @property */
    public void set_LastName(String value)
    {
        lastName = value;
    } //set_LastName


    private String firstName;


    /** @property */
    public String get_FirstName()
    {
        return firstName;
    } //get_FirstName


    /** @property */
    public void set_FirstName(String value)
    {
        firstName = value;
    } //set_FirstName


    /** @property */
    public String get_FullName()
    {
        return firstName + " " + lastName;
    } //get_FullName


    private String address;


    /** @property */
    public String get_Address()
    {
        return address;
    } //get_Address


    /** @property */
    public void set_Address(String value)
    {
        address = value;
    } //set_Address
} //NorthwindEmployee

Windows 98, Windows 2000 SP4, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see System Requirements.

.NET Framework

Supported in: 2.0
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