DropDownList DataBind Creates Duplicate Values _ the Official Microsoft ASP

7/10/13 DropDownList DataBind creates duplicate values : The Official Microsoft ASP.NET Forums

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DropDownList DataBind creates duplicate valuesRSS

18 replies

Last post Oct 30, 2009 01:52 AM by decker dong - msft



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ppalubinski

Member

49 Points

175 Posts

DropDownList DataBind creates duplicate values

Oct 22, 2009 03:48 PM|LINK

So I've had this problem come up a few times, and it drives me crazy. I have a form with a dropdownlist thatpopulates from a database. There are other controls on the form which cause an autopostback. However, Ineed to re-bind the dropdownlist each time because there is a databound event attached to its datasource. Whenthis happens, it creates duplicate values in the dropdownlist. Does anyone know how to get around this?

protected void ddlLessors_SelectedIndexChanged(object sender, EventArgs e) { if (ddlLessors.SelectedIndex > 0) { Wizard1.MoveTo(Wizard1.WizardSteps[Wizard1.ActiveStepIndex + 1]);

this.SetDropDownList((DropDownList)sender);

ddlProspects.DataBind(); } }

protected void ddlProspects_DataBound(object sender, EventArgs e) { using (DbConnection dbConnection = this.dbProviderFactory.CreateConnection()) { dbConnection.ConnectionString = this.connString; dbConnection.Open();

DbCommand dbCommand = dbConnection.CreateCommand();

dbCommand.CommandText = "SELECT TOP 1 p.ProspectCode FROMACCOUNTING.PROSPECT p " + "INNER JOIN ACCOUNTING.PROSPECT_TRACT p_t ON p.ProspectCode =p_t.ProspectCode " + "INNER JOIN LANDMAN.TRACT t ON p_t.TractId = t.TractId " +



"INNER JOIN LANDMAN.LEASE le ON t.TractId = le.TractId " + "INNER JOIN LANDMAN.LESSOR l ON le.LessorId = l.LessorId " + "WHERE l.LessorId = @LessorId; ";

dbCommand.Parameters.Add(new SqlParameter("@LessorId", ddlLessors.SelectedValue));

ddlProspects.SelectedValue = (string)dbCommand.ExecuteScalar(); } }

DropDownList databound

"Do your damnedest in an ostentatious manner all the time."

Moved by SGWellens on Oct 22, 2009 05:40 PMReply

astahir

Member

512 Points

118 Posts

Re: DropDownList DataBind creates duplicate values

Oct 23, 2009 06:43 AM|LINK

There must be better ways of doing this but one way around could be to delete all items of the DropDownListbefore its DataBind, i.e.

//Clear existing items if (DropDownList1.Items.Count > 0) { DropDownList1.Items.Clear(); } //Bind DropDownList here

Reply

Ahmish

Participant

1084 Points



312 Posts


Oct 23, 2009 06:53 AM|LINK

Why are you rebinding your dropdownlist on each postback? Once you bound your dropdownlist, the view stateof dropdowlist will persist values on post backs you dont need to rebind.

Your code should look like this.

if (!IsPostBack) {

ddlUser.DataTextField = "User_Name"; ddlUser.DataValueField = "User_Code"; ddlUser.DataSource = GetDataTable(); ddlIssueToUser.DataBind();

}

Hope it will help you out :)

"Hope its your Solution so Mark it as Answer"

Ahmad Sheikh Microsoft Valuable Geek :: Freelancer & Consultant http://sharpcontents.blogspot.com

Reply

ppalubinski

Member

49 Points

175 Posts


Oct 23, 2009 03:00 PM|LINK

Well, one thing is that it needs to select a specific value in the dropdownlist based on a database query. So eachtime there is any kind of autopostback, I need to make sure that the right item is still selected. I just stuck it in thedatabound event for the dropdownlist because I didn't know where else to put it. Also, I have a fewdropdownlists that are dependent on the values selected in other dropdownlists before being populated... A usercan go back and change the value of an earlier dropdownlist. If so, then it must rebind the dependentdropdownlist(s).

"Do your damnedest in an ostentatious manner all the time."Reply



ppalubinski

Member

49 Points

175 Posts


Oct 23, 2009 03:03 PM|LINK

Thanks. I've tried to call the clear() method in Page_Load, but it didn't seem to fix the problem. But I think I'mjust calling it in the wrong place. I'll tinker around some more and try find a better place to put it...


tamilcodes

Contributor

3140 Points

690 Posts


Oct 23, 2009 04:05 PM|LINK

This is happens when ur viewstate is set to true,

and you are databinding the dropdownlist again and again on every postback,

paste your code for the first ddl

SITE STATISTICS LITE - www.tamilcodes.com

TUTORIAL RIVER - HTML, ASP.NET, PHOTOSHOP, WEB DESIGN TUTORIALSEdited by tamilcodes on Oct 23, 2009 04:06 PMReply



ppalubinski

Member

49 Points

175 Posts


Oct 23, 2009 04:41 PM|LINK

Here's all my code beside stuff:

public partial class _Default : System.Web.UI.Page { private DbProviderFactory dbProviderFactory; private string connString = WebConfigurationManager.ConnectionStrings["TcoConnString"].ConnectionString; private string factory = "System.Data.SqlClient";

protected void Page_Load(object sender, EventArgs e) { this.dbProviderFactory = DbProviderFactories.GetFactory(this.factory); }

protected void ddlNext_SelectedIndexChanged(object sender, EventArgs e) { DropDownList ddl = (DropDownList)sender;

if (ddl.SelectedIndex > 0) { Wizard1.MoveTo(Wizard1.WizardSteps[Wizard1.ActiveStepIndex + 1]); this.Wizard1_NextButtonClick(sender, new WizardNavigationEventArgs(Wizard1.ActiveStepIndex - 1, Wizard1.ActiveStepIndex)); } }

protected void ddlProspects_SelectedIndexChanged(object sender, EventArgs e) { if (ddlLessors.SelectedIndex > 0) { ddlLeases.Enabled = true; lbAddTract.Enabled = true;

pnlAddTract.Visible = false; } else { ddlLeases.Enabled = false; lbAddTract.Enabled = false;



pnlAddTract.Visible = true; }

ddlLeases.DataBind(); }

protected void lbAddLessor_Click(object sender, EventArgs e) { pnlAddLessor.Visible = true; ddlLessors.Enabled = false; ddlLessors.SelectedIndex = 0; lbAddLessor.Enabled = false; }

protected void lbClearLessor_Click(object sender, EventArgs e) { pnlAddLessor.Controls.Clear(); pnlAddLessor.Visible = false; ddlLessors.Enabled = true; lbAddLessor.Enabled = true; }

protected void lbAddTract_Click(object sender, EventArgs e) { pnlAddTract.Visible = true; ddlProspects.Enabled = true; ddlLeases.Enabled = false; lbAddTract.Enabled = false; }

protected void Wizard1_NextButtonClick(object sender, WizardNavigationEventArgs e) { switch (e.CurrentStepIndex) { case 0: if (ddlLessors.SelectedIndex > 0) { ddlLeases.Enabled = true; lbAddTract.Enabled = true; pnlAddTract.Visible = false; } else { ddlProspects.SelectedIndex = 0; ddlLeases.SelectedIndex = 0;

ddlLeases.Enabled = false; lbAddTract.Enabled = false; pnlAddTract.Visible = true; }

ddlProspects.DataBind();



ddlLeases.DataBind(); break; } }

protected void ddlProspects_DataBound(object sender, EventArgs e) { using (DbConnection dbConnection = this.dbProviderFactory.CreateConnection()) { dbConnection.ConnectionString = this.connString; dbConnection.Open();

DbCommand dbCommand = dbConnection.CreateCommand();

dbCommand.CommandText = "SELECT TOP 1 p.ProspectCode FROMACCOUNTING.PROSPECT p " + "INNER JOIN ACCOUNTING.PROSPECT_TRACT p_t ON p.ProspectCode =p_t.ProspectCode " + "INNER JOIN LANDMAN.TRACT t ON p_t.TractId = t.TractId " + "INNER JOIN LANDMAN.LEASE le ON t.TractId = le.TractId " + "INNER JOIN LANDMAN.LESSOR l ON le.LessorId = l.LessorId " + "WHERE l.LessorId = @LessorId; ";

dbCommand.Parameters.Add(new SqlParameter("@LessorId", ddlLessors.SelectedValue));

string prospectCode = (string)dbCommand.ExecuteScalar();

if (!string.IsNullOrEmpty(prospectCode)) { ddlProspects.SelectedValue = prospectCode; } else { ddlLeases.Enabled = false; } } }

protected void ddlLeases_DataBinding(object sender, EventArgs e) { dsLeases.SelectParameters["LessorId"].DefaultValue = ddlLessors.SelectedValue; dsLeases.SelectParameters["ProspectCode"].DefaultValue = ddlProspects.SelectedValue; }

protected void ddlLeases_DataBound(object sender, EventArgs e) { if (ddlLeases.Items.Count == 0) {

} } }



And here's all the markup:

Lessor:



First Name: Last Name: Middle Name: Company/Entity Name: Prospect:



Lease:




sassyboy

Member

728 Points

322 Posts


Oct 23, 2009 07:01 PM|LINK

Seems you need to use a Cascading DropdownList of the asp.net ajax control toolkit

http://www.asp.net/AJAX/AjaxControlToolkit/Samples/CascadingDropDown/CascadingDropDown.aspx

http://www.asp.net/AJAX/AjaxControlToolkit/Samples/Walkthrough/CCDWithDB.aspx

http://www.asp.net/Learn/ajax-videos/video-77.aspx

Thanks

S@ss (Shashi Shekhar Singh)



My Blog

Please mark a post as ANSWER if that post helped resolve your query.Reply

ppalubinski

Member

49 Points

175 Posts


Oct 23, 2009 07:48 PM|LINK

Okay, I tinkered around with the cascadingdropdown and it seems to be a good approach. The only problem is

that I still need to it do an autopostback because I need to use the OnSelectedIndexChanged event to triggersome other actions. Also, when it does post back to the server, it doesn't seem to know what the state is of the

dropdownlist (says SelectedIndex is 0 when it isn't)... Have you come across this problem?

[WebMethod] public AjaxControlToolkit.CascadingDropDownNameValue[]

GetDropDownLessors(string knownCategoryValues, string category) {

using (SqlConnection conn = new SqlConnection( WebConfigurationManager.ConnectionStrings["TcoConnString"].ConnectionString))

{ conn.Open();



string query = "SELECT LessorId, (LastName + ', ' + FirstName + ' ' + ISNULL(MiddleName,''))Name FROM LANDMAN.LESSOR " +

"ORDER BY Name ASC; ";

SqlCommand cmd = new SqlCommand(query, conn);

SqlDataAdapter da = new SqlDataAdapter(cmd); DataSet ds = new DataSet();

da.Fill(ds);

List cascadingDropDownNameValues = new List();

foreach (DataRow dr in ds.Tables[0].Rows)

{ string lessorId = dr["LessorId"].ToString();

string name = dr["Name"].ToString();

cascadingDropDownNameValues.Add( new AjaxControlToolkit.CascadingDropDownNameValue(name, lessorId));

}

return cascadingDropDownNameValues.ToArray(); }

}


Reply

ppalubinski

Member

49 Points

175 Posts


Oct 23, 2009 07:51 PM|LINK

Also, is it possible to set the SelectedValue property on the CascadingDropDown control dynamically (based onanother database query)?


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