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Making C# code generate webform with Events

protected void Page_Load(object sender, EventArgs e)
{
if (Request.QueryString.Count > 0)
{
DataTable dt = new DataTable();
SqlDataAdapter adapter = new SqlDataAdapter("select * from personalization where ponumber = '" + Request.QueryString["PO"] + "'", VisualConnect);
adapter.Fill(dt);
if (dt.Rows.Count > 0)
{
for (Int32 i = 0; i < dt.Rows.Count; i++)
{
HtmlGenericControl tr = new HtmlGenericControl("tr");
HtmlGenericControl td = new HtmlGenericControl("td");
HtmlGenericControl td1 = new HtmlGenericControl("td");
Label lbcustomename = new Label();
lbcustomename.ID = "lbline1";
lbcustomename.Text = "Recipient Name: ";
td.Controls.Add(lbcustomename);
tr.Controls.Add(td);
TextBox txtcustombox = new TextBox();
txtcustombox.ID = "txtline1";
txtcustombox.Text = dt.Rows[i]["line1"].ToString();
td1.Controls.Add(txtcustombox);
tr.Controls.Add(td1);
placeholder.Controls.Add(tr);
//Add button after last record
if (i == dt.Rows.Count - 1)
{
tr = new HtmlGenericControl("tr");
td = new HtmlGenericControl("td");
Button btnSubmit = new Button();
btnSubmit.ID = "btnSubmit";
btnSubmit.Click += btnSubmit_Click;
btnSubmit.Text = "Submit";
btnSubmit.Attributes.Add("runat", "server");
td.Controls.Add(btnSubmit);
td.Attributes.Add("Colspan", "2");
td.Attributes.Add("style", "text-align:center;");
tr.Controls.Add(td);
placeholder.Controls.Add(tr);
}
}
}
}
}
private void btnSubmit_Click(object sender, EventArgs e)
{
// do something
}
}
I have added this code to dynamically draw up fields from a database for input where the user would click the Submit button when completed. However, whenever I click the submit button, it wants to reload the page and the btnSubmit_Click event is never invoked instead. Am I missing something?

How to do OnClick on selected item in "dynamic" ASP.NET DropDownList without using JavaScript

Currently, there is 2 values in my DropDownList which is viewProduct and editProduct. So when the user selects one of the value, it will direct user to the particular function in ASP.NET. I have tried OnSelectedIndexChanged, but it seems like not working on the dynamic DropDownList.
Here is my code:
ddlAction.ID = "ddlForAction";
ddlAction.CssClass = "ddlList";
ddlAction.CausesValidation = false;
ddlAction.AutoPostBack = true;
ddlAction.Items.Add(new ListItem("View","viewProduct"));
ddlAction.Items.Add(new ListItem("Edit", "editProduct"));
e.Row.Cells[5].Controls.Add(ddlAction);
if(ddlAction.SelectedValue == "editProduct")
{
editProduct();
}
else if(ddlAction.SelectedValue == "viewProduct")
{
retrieveProduct();
}
Any idea how to solve it without using JavaScript?
My entire code:
protected void Page_Load(object sender, EventArgs e)
{
BindGridView();
}
private void BindGridView()
{
MySqlConnection conn = new MySqlConnection(sqlConn);
string sql = "SELECT prodID, prodName, stockLevel, reorderLevel, unitPrice from Product";
MySqlCommand cmd = new MySqlCommand(sql, conn);
MySqlDataAdapter sda = new MySqlDataAdapter(cmd);
DataTable dt = new DataTable();
sda.Fill(dt);
productList.DataSource = dt;
productList.DataBind();
}
protected void GridView_RowDataBound(object sender, GridViewRowEventArgs e)
{
TableCell tc = new TableCell();
DropDownList ddlAction = new DropDownList();
if (e.Row.RowType == DataControlRowType.Header)
{
e.Row.Cells[0].Text = "Prod ID";
e.Row.Cells[1].Text = "Product Name";
e.Row.Cells[2].Text = "Qty";
e.Row.Cells[3].Text = "Reorder Level";
e.Row.Cells[4].Text = "Price (RM)";
e.Row.Controls.Add(tc);
}
if (e.Row.RowType == DataControlRowType.DataRow)
{
var qty = Int16.Parse(e.Row.Cells[2].Text);
var reorder = Int16.Parse(e.Row.Cells[3].Text);
if (qty <= reorder)
{
e.Row.Cells[2].CssClass = "redCell";
e.Row.Cells[3].CssClass = "redCell";
}
e.Row.Controls.Add(tc);
ddlAction.ID = "ddlForAction";
ddlAction.CssClass = "ddlList";
ddlAction.CausesValidation = false;
ddlAction.AutoPostBack = true;
ddlAction.Items.Add(new ListItem("View","viewProduct"));
ddlAction.Items.Add(new ListItem("Edit", "editProduct"));
e.Row.Cells[5].Controls.Add(ddlAction);
ddlAction.SelectedIndexChanged += DDLAction_OnSelectedIndexChanged;
if (ddlAction.SelectedValue == "editProduct")
{
editProduct();
}
else if (ddlAction.SelectedValue == "viewProduct")
{
retrieveProduct();
}
}
}

You need to declare an event handler then assign it to the control before adding the control to the page.
Here is an example :
protected void Page_Load(object sender, EventArgs e)
{
if(!Page.IsPostBack)
{
CreateControl();
}
}
protected void CreateControl()
{
var ddlAction = new DropDownList();
ddlAction.ID = "ddlForAction";
ddlAction.CssClass = "ddlList";
ddlAction.CausesValidation = false;
ddlAction.AutoPostBack = true;
ddlAction.Items.Add(new ListItem("View","viewProduct"));
ddlAction.Items.Add(new ListItem("Edit", "editProduct"));
ddlAction.SelectedIndexChanged += DDLAction_OnSelectedIndexChanged;
e.Row.Cells[5].Controls.Add(ddlAction);
}
protected void DDLAction_OnSelectedIndexChanged(object sender, EventArgs e)
{
var action = (DropDownList) sender;
var choice = action.SelectedValue?.Trim();
string script = null;
switch (choice)
{
case "viewProduct":
script = "alert('View page!');";
break;
case "editProduct":
script = "alert('Edit page!');";
break;
default:
script = "alert('Unmatched Value!')";
break;
}
ScriptManager.RegisterStartupScript(this , typeof(_Default) , "TestJS" , $"<script>{script}</script>" , false);
}
use ScriptManager.RegisterStartupScript when you want to work with JS scripts. Response.Write will not parse script blocks as an executable blocks. It will throw a parse error though (you could check the browser console.

How to check that Dynamically created checkbox checked or not?

I've created some dynamic checkboxes in table header row.
If the checkbox is checked , table will have another row with a textbox.
Checkbox changed event is firing very well but when I'm trying to check whether the checkbox is checked or not , it's generating exception :
Object Reference not set to an instance of an object.
Here is my code :
Creating Dynamic controls here :
TableRow thead = new TableRow();
for (int i = 0; i < dt_fundtype.Rows.Count; i++)
{
TableCell td = new TableCell();
CheckBox chk = new CheckBox();
chk.ID = "fund_" + dt_fundtype.Rows[i]["fund_type_cd"];
chk.Text = dt_fundtype.Rows[i]["fund_type"].ToString();
chk.AutoPostBack = true;
chk.CheckedChanged += new EventHandler(Chk_Fund_CheckedChange);
td.Controls.Add(chk);
thead.Cells.Add(td);
}
tbl_fundtype.Rows.Add(thead);
Checkbox checked changed event :
public void Chk_Fund_CheckedChange(object sender, EventArgs e)
{
TableRow tr = new TableRow();
for (int i=0;i<tbl_fundtype.Rows[0].Cells.Count;i++)
{
string DynamicChkID ="fund_"+ dt_fundtype.Rows[i]["fund_type_cd"].ToString();
CheckBox chk = new CheckBox();
chk = (CheckBox)tbl_fundtype.Rows[0].Cells[i].FindControl("DynamicChkID");
if (chk.Checked == true)//Here is the Exception
{
TableCell td = new TableCell();
td.Text = "Test";
tr.Cells.Add(td);
}
}
tbl_fundtype.Rows.Add(tr);
hfTab.Value = "fund";
collapsestate = "expand";
}
The event is firing very well , but when I check that the checkbox is checked or not there's an exception.
How can I resolve this problem ? Kindly Help me Please

This is the example I use which work for me.
I've simplified the binding logic and lookup logic etc, to illustrate
protected void Page_Load(object sender, EventArgs e)
{
AddStuff();
}
private void AddStuff()
{
TableRow thead = new TableRow();
for (int i = 0; i < 10; i++)
{
TableCell td = new TableCell();
CheckBox chk = new CheckBox();
chk.ID = "fund_" + i;
chk.Text = i.ToString();
chk.AutoPostBack = true;
chk.CheckedChanged += new EventHandler(Chk_Fund_CheckedChange);
td.Controls.Add(chk);
thead.Cells.Add(td);
}
tbl_fundtype.Rows.Add(thead);
}
public void Chk_Fund_CheckedChange(object sender, EventArgs e)
{
for (int i = 0; i < 10; i++)
{
var chk = tbl_fundtype.FindControl("fund_" + i) as CheckBox;
if (chk.Checked)
{
//I am checked
}
}
}
And on my markup page I have:
<asp:Table ID="tbl_fundtype" runat="server" />

protected void Page_Load(object sender, EventArgs e)
{
DataTable dt = Rowcreation();
TableRow thead = new TableRow();
for (int i = 0; i < dt.Rows.Count; i++)
{
TableCell td = new TableCell();
CheckBox chk = new CheckBox();
chk.ID = "fund" + dt.Rows[i]["ID"];
chk.Text = dt.Rows[i]["Name"].ToString();
chk.AutoPostBack = true;
chk.CheckedChanged += new EventHandler(chk_fun_checkedchange);
td.Controls.Add(chk);
thead.Controls.Add(td);
}
pnl.Controls.Add(thead);
}
public void chk_fun_checkedchange(object sender, EventArgs e)
{
DataTable dt = Rowcreation();
for (int i = 0; i < dt.Rows.Count; i++)
{
CheckBox chkbx = (CheckBox ) pnl.Parent.Controls[0].FindControl("fund"+dt.Rows [i]["ID"]);
if (chkbx.Checked == true)
{
lbl.Text = chkbx.Text;
}
}
}
private DataTable Rowcreation()
{
DataTable dt = new DataTable();
dt.Columns.Add("ID");
dt.Columns.Add("Name");
DataRow dr = dt.NewRow();
dr["ID"] = "1";
dr["Name"] = "Name1";
dt.NewRow();
dt.Rows.Add(dr);
DataRow dr1 = dt.NewRow();
dr1["ID"] = "2";
dr1["Name"] = "Name2";
dt.Rows.Add(dr1);
dt.NewRow();
DataRow dr2 = dt.NewRow();
dr2["ID"] = "3";
dr2["Name"] = "Name3";
dt.Rows.Add(dr2);
return dt;
}

Dynamically added gridview's linkbutton not working

I have a gridview that has dynamically created columns.
Right now all the data is showing in its respective place but I am unable to get my link button to work. (Gridview disappears)
Here is my backend code, the gridview used is just an empty gridview
protected void Page_Load(object sender, EventArgs e)
{
if (!this.IsPostBack)
{
TemplateField tfield = new TemplateField();
tfield.HeaderText = "View";
GridView1.Columns.Add(tfield);
}
GridView1.DataBind();
}
string selectedID = null;
private void BindGrid(List<string> SelectedInfo)
{
DataTable dt = new DataTable();
//Dynamically adding columns and setting first column added as ID
selectedID = SelectedInfo[0];
for (int i = 0; i < SelectedInfo.Count; i++)
{
dt.Columns.Add(new DataColumn(SelectedInfo[i], typeof(string)));
}
List<string[]> InfoList = getInfoList(SelectedInfo);
for (int i = 0; i < InfoList.Count; i++)
{
dt.Rows.Add(InfoList[i]);
}
GridView1.DataSource = dt;
GridView1.DataBind();
}
protected void GridView1_RowDataBound(object sender, GridViewRowEventArgs e)
{
if (e.Row.RowType == DataControlRowType.DataRow)
{ //Adding link button to first column
LinkButton lnkView = new LinkButton();
lnkView.ID = "lnkView";
lnkView.Text = "View";
lnkView.Click += ViewDetails;
lnkView.CommandArgument = (e.Row.DataItem as DataRowView).Row[selectedID].ToString();
e.Row.Cells[0].Controls.Add(lnkView);
}
}
protected void ViewDetails(object sender, EventArgs e)
{
//Popup the selected row ID
LinkButton lnkView = (sender as LinkButton);
GridViewRow row = (lnkView.NamingContainer as GridViewRow);
string id = lnkView.CommandArgument;
ClientScript.RegisterStartupScript(this.GetType(), "alert", "alert('Row ID" + id + "')", true);
}
protected void CheckBoxList2_SelectedIndexChanged(object sender, EventArgs e)
{
List<string> SelectedInfo = new List<string>();
for (int i = 0; i < CheckBoxList2.Items.Count; i++)
{
if (CheckBoxList2.Items[i].Selected)
{
SelectedInfo.Add(CheckBoxList2.Items[i].Text);
}
}
BindGrid(SelectedInfo);
}

If you need to create controls at runtime, you better use the RowCreated event:
protected void GridView1_RowCreated(object sender, GridViewRowEventArgs e)
{
if (e.Row.RowType == DataControlRowType.DataRow)
{ //Adding link button to first column
LinkButton lnkView = new LinkButton();
lnkView.ID = "lnkView";
lnkView.Text = "View";
lnkView.Click += ViewDetails;
lnkView.CommandArgument = (e.Row.DataItem as DataRowView).Row[selectedID].ToString();
e.Row.Cells[0].Controls.Add(lnkView);
}
}
Otherwise you have to bind your GridView on every postback inViewDetails the Page_Load event.
Anyway if your GridView disappears, it's just because you have to bind it again in the ViewDetails method.

I hope below code will help you.
protected void Page_Load(object sender, EventArgs e)
{
if (!this.IsPostBack)
{
TemplateField tfield = new TemplateField();
tfield.HeaderText = "View";
GridView1.Columns.Add(tfield);
}
this.BindGrid();
}
private void BindGrid()
{
DataTable dt = new DataTable();
dt.Columns.AddRange(new DataColumn[2] { new DataColumn("Id", typeof(int)),
new DataColumn("Name", typeof(string)) });
dt.Rows.Add(1, "A");
dt.Rows.Add(2, "B");
GridView1.DataSource = dt;
GridView1.DataBind();
}
protected void OnRowDataBound(object sender, GridViewRowEventArgs e)
{
if (e.Row.RowType == DataControlRowType.DataRow)
{
LinkButton lnkView = new LinkButton();
lnkView.ID = "lnkView";
lnkView.Text = "View";
lnkView.Click += ViewDetails;
lnkView.CommandArgument = (e.Row.DataItem as DataRowView).Row["Id"].ToString();
e.Row.Cells[2].Controls.Add(lnkView);
}
}
protected void ViewDetails(object sender, EventArgs e)
{
LinkButton lnkView = (sender as LinkButton);
GridViewRow row = (lnkView.NamingContainer as GridViewRow);
string id = lnkView.CommandArgument;
ClientScript.RegisterStartupScript(this.GetType(), "alert", "alert('Id: " + id + "')", true);
}

Dropdownlist does not update after adding update panel

I have multiple dropdownlist box all querying the same column, same table and from the same database. For example under memberID column i have the following IDs.
12345
23456
34567
And i have 3 different dropdownlist box as shown below
<asp:DropDownList ID="memberID3" runat="server" Visible="false" OnSelectedIndexChanged="ddlpid3_SelectedIndexChanged" >
</asp:DropDownList>
<asp:DropDownList ID="memberID1" runat="server" Visible="false" OnSelectedIndexChanged="ddlpid1_SelectedIndexChanged">
</asp:DropDownList>
<asp:DropDownList ID="memberID2" runat="server" Visible="false" OnSelectedIndexChanged="ddlpid2_SelectedIndexChanged">
</asp:DropDownList>
I added update panel between the dropdownlist so as to allow my dropdownlist to refresh upon any updates/selections.
<asp:UpdatePanel ID="UpdatePanel1" runat="server">
<ContentTemplate>
</ContentTemplate>
</asp:UpdatePanel>
For instance, when memberID1 selected 12345, the other 2 dropdownlist (memberID2 and 3) will not display the ID 12345. Vice versa, when memberID1 select the default value of the dropdownlist, the ID reappears in the other 2 dropdownlistbox. I have added a default value for all of the DDL.
memeberID(number).Items.Insert(0, new ListItem(" Please select a Member ID", ""));
memeberID(number).SelectedIndex = 0;
If i have not mistaken the property of update panel, isn't that able to make this function work?
here is the binding code as requested.
protected void ddllocation_SelectedIndexChanged(object sender, EventArgs e)
{
using (var connAdd = new SqlConnection("Data Source = localhost; Initial Catalog = MajorProject; Integrated Security= SSPI"))
{
connAdd.Open();
var sql = "Select policeid from PoliceAccount where status ='available' and handle ='offcase' and postedto='" + ddllocation.SelectedValue + "'";
using (var cmdAdd = new SqlDataAdapter(sql, connAdd))
{
DataSet ds2 = new DataSet();
cmdAdd.Fill(ds2);
memberID1.Items.Clear();
memberID1.DataSource = ds2;
memberID1.DataTextField = "memberID";
memberID1.DataValueField = "memberID";
memberID1.DataBind();
memberID1.Items.Insert(0, new ListItem("Please select a Member ID", ""));
memberID1.SelectedIndex = 0;
memberID2.Items.Clear();
memberID2.DataSource = ds2;
memberID2.DataTextField = "memberID";
memberID2.DataValueField = "memberID";
memberID2.DataBind();
memberID2.Items.Insert(0, new ListItem("Please select a Member ID", ""));
memberID2.SelectedIndex = 0;
memberID3.Items.Clear();
memberID3.DataSource = ds2;
memberID3.DataTextField = "memberID";
memberID3.DataValueField = "memberID";
memberID3.DataBind();
memberID3.Items.Insert(0, new ListItem("Please select a Member ID", ""));
memberID3.SelectedIndex = 0;
}
UPDATE
For now i'm able to allow my other ddl to re-bind and cache the selected value in the other dropdownlist when the default value is selected. However, when i select other ID, the ID are being removed and it wont re-bind the other ddl.
protected void FillddlLocations()
{
FillDropdown(ddlpid1);
FillDropdown(ddlpid2);
FillDropdown(ddlpid3);
FillDropdown(ddlpid4);
FillDropdown(ddlpid5);
ddlpid1.Visible = false;
ddlpid2.Visible = false;
ddlpid3.Visible = false;
ddlpid4.Visible = false;
ddlpid5.Visible = false;
}
protected void FillDropdown(DropDownList ddl)
{
using (var connAdd = new SqlConnection("Data Source = localhost; Initial Catalog = MajorProject; Integrated Security= SSPI"))
{
connAdd.Open();
var sql = "Select policeid from PoliceAccount where status ='available' and handle ='offcase' and postedto='" + ddllocation.SelectedValue + "'";
using (var cmdAdd = new SqlDataAdapter(sql, connAdd))
{
DataSet ds2 = new DataSet();
cmdAdd.Fill(ds2);
ddl.Items.Clear();
ddl.DataSource = ds2;
ddl.DataBind();
ddl.Items.Insert(0, new ListItem("Police ID", ""));
ddl.SelectedIndex = 0;
}
}
}
protected void ddlpid1_SelectedIndexChanged(object sender, EventArgs e)
{
if (ddlpid1.SelectedIndex > 0)
{
Session["pid1"] = ddlpid1.SelectedValue;
ListItem removeItem2 = ddlpid2.Items.FindByValue(ddlpid1.SelectedValue);
ddlpid2.Items.Remove(removeItem2);
ListItem removeItem3 = ddlpid3.Items.FindByValue(ddlpid1.SelectedValue);
ddlpid3.Items.Remove(removeItem3);
ListItem removeItem4 = ddlpid4.Items.FindByValue(ddlpid1.SelectedValue);
ddlpid4.Items.Remove(removeItem4);
ListItem removeItem5 = ddlpid5.Items.FindByValue(ddlpid1.SelectedValue);
ddlpid5.Items.Remove(removeItem5);
}
else
if (ddlpid1.SelectedItem.Text.Equals("Police ID"))
{
FillDropdown(ddlpid1);
FillDropdown(ddlpid2);
FillDropdown(ddlpid3);
FillDropdown(ddlpid4);
FillDropdown(ddlpid5);
ddlpid2.SelectedValue = (String)Session["pid2"];
ddlpid2_SelectedIndexChanged(this, EventArgs.Empty);
ddlpid3.SelectedValue = (String)Session["pid3"];
ddlpid3_SelectedIndexChanged(this, EventArgs.Empty);
ddlpid4.SelectedValue = (String)Session["pid4"];
ddlpid4_SelectedIndexChanged(this, EventArgs.Empty);
ddlpid5.SelectedValue = (String)Session["pid5"];
ddlpid5_SelectedIndexChanged(this, EventArgs.Empty);
}
}
protected void ddlpid2_SelectedIndexChanged(object sender, EventArgs e)
{
if (ddlpid2.SelectedIndex > 0)
{
Session["pid2"] = ddlpid2.SelectedValue;
ListItem removeItem1 = ddlpid1.Items.FindByValue(ddlpid2.SelectedValue);
ddlpid1.Items.Remove(removeItem1);
ListItem removeItem3 = ddlpid3.Items.FindByValue(ddlpid2.SelectedValue);
ddlpid3.Items.Remove(removeItem3);
ListItem removeItem4 = ddlpid4.Items.FindByValue(ddlpid2.SelectedValue);
ddlpid4.Items.Remove(removeItem4);
ListItem removeItem5 = ddlpid5.Items.FindByValue(ddlpid2.SelectedValue);
ddlpid5.Items.Remove(removeItem5);
}
else if (ddlpid2.SelectedItem.Text.Equals("Police ID"))
{
FillDropdown(ddlpid1);
FillDropdown(ddlpid2);
FillDropdown(ddlpid3);
FillDropdown(ddlpid4);
FillDropdown(ddlpid5);
ddlpid1.SelectedValue = (String)Session["pid1"];
ddlpid1_SelectedIndexChanged(this, EventArgs.Empty);
ddlpid3.SelectedValue = (String)Session["pid3"];
ddlpid3_SelectedIndexChanged(this, EventArgs.Empty);
ddlpid4.SelectedValue = (String)Session["pid4"];
ddlpid4_SelectedIndexChanged(this, EventArgs.Empty);
ddlpid5.SelectedValue = (String)Session["pid5"];
ddlpid5_SelectedIndexChanged(this, EventArgs.Empty);
}
}
protected void ddlpid3_SelectedIndexChanged(object sender, EventArgs e)
{
if (ddlpid3.SelectedIndex > 0)
{
Session["pid3"] = ddlpid3.SelectedValue;
ListItem removeItem1 = ddlpid1.Items.FindByValue(ddlpid3.SelectedValue);
ddlpid1.Items.Remove(removeItem1);
ListItem removeItem2 = ddlpid2.Items.FindByValue(ddlpid3.SelectedValue);
ddlpid2.Items.Remove(removeItem2);
ListItem removeItem4 = ddlpid4.Items.FindByValue(ddlpid3.SelectedValue);
ddlpid4.Items.Remove(removeItem4);
ListItem removeItem5 = ddlpid5.Items.FindByValue(ddlpid3.SelectedValue);
ddlpid5.Items.Remove(removeItem5);
}
else if (ddlpid3.SelectedItem.Text.Equals("Police ID"))
{
FillDropdown(ddlpid1);
FillDropdown(ddlpid2);
FillDropdown(ddlpid3);
FillDropdown(ddlpid4);
FillDropdown(ddlpid5);
ddlpid1.SelectedValue = (String)Session["pid1"];
ddlpid1_SelectedIndexChanged(this, EventArgs.Empty);
ddlpid2.SelectedValue = (String)Session["pid2"];
ddlpid2_SelectedIndexChanged(this, EventArgs.Empty);
ddlpid4.SelectedValue = (String)Session["pid4"];
ddlpid4_SelectedIndexChanged(this, EventArgs.Empty);
ddlpid5.SelectedValue = (String)Session["pid5"];
ddlpid5_SelectedIndexChanged(this, EventArgs.Empty);
}
}
protected void ddlpid4_SelectedIndexChanged(object sender, EventArgs e)
{
if (ddlpid4.SelectedIndex > 0)
{
Session["pid4"] = ddlpid4.SelectedValue;
ListItem removeItem1 = ddlpid1.Items.FindByValue(ddlpid4.SelectedValue);
ddlpid1.Items.Remove(removeItem1);
ListItem removeItem2 = ddlpid2.Items.FindByValue(ddlpid4.SelectedValue);
ddlpid2.Items.Remove(removeItem2);
ListItem removeItem3 = ddlpid3.Items.FindByValue(ddlpid4.SelectedValue);
ddlpid3.Items.Remove(removeItem3);
ListItem removeItem5 = ddlpid5.Items.FindByValue(ddlpid4.SelectedValue);
ddlpid5.Items.Remove(removeItem5);
}
else if (ddlpid4.SelectedItem.Text.Equals("Police ID"))
{
FillDropdown(ddlpid1);
FillDropdown(ddlpid2);
FillDropdown(ddlpid3);
FillDropdown(ddlpid4);
FillDropdown(ddlpid5);
ddlpid1.SelectedValue = (String)Session["pid1"];
ddlpid1_SelectedIndexChanged(this, EventArgs.Empty);
ddlpid2.SelectedValue = (String)Session["pid2"];
ddlpid2_SelectedIndexChanged(this, EventArgs.Empty);
ddlpid3.SelectedValue = (String)Session["pid3"];
ddlpid3_SelectedIndexChanged(this, EventArgs.Empty);
ddlpid5.SelectedValue = (String)Session["pid5"];
ddlpid5_SelectedIndexChanged(this, EventArgs.Empty);
}
}
protected void ddlpid5_SelectedIndexChanged(object sender, EventArgs e)
{
if (ddlpid5.SelectedIndex > 0)
{
Session["pid5"] = ddlpid5.SelectedValue;
ListItem removeItem1 = ddlpid1.Items.FindByValue(ddlpid5.SelectedValue);
ddlpid1.Items.Remove(removeItem1);
ListItem removeItem2 = ddlpid2.Items.FindByValue(ddlpid5.SelectedValue);
ddlpid2.Items.Remove(removeItem2);
ListItem removeItem3 = ddlpid3.Items.FindByValue(ddlpid5.SelectedValue);
ddlpid3.Items.Remove(removeItem3);
ListItem removeItem4 = ddlpid4.Items.FindByValue(ddlpid5.SelectedValue);
ddlpid4.Items.Remove(removeItem4);
}
else if (ddlpid5.SelectedItem.Text.Equals("Police ID"))
{
FillDropdown(ddlpid1);
FillDropdown(ddlpid2);
FillDropdown(ddlpid3);
FillDropdown(ddlpid4);
FillDropdown(ddlpid5);
ddlpid1.SelectedValue = (String)Session["pid1"];
ddlpid1_SelectedIndexChanged(this, EventArgs.Empty);
ddlpid2.SelectedValue = (String)Session["pid2"];
ddlpid2_SelectedIndexChanged(this, EventArgs.Empty);
ddlpid3.SelectedValue = (String)Session["pid3"];
ddlpid3_SelectedIndexChanged(this, EventArgs.Empty);
ddlpid4.SelectedValue = (String)Session["pid4"];
ddlpid4_SelectedIndexChanged(this, EventArgs.Empty);
}
}

First of all, I would set the AutoPostBack property for dropdowns to true in my markup:
<asp:DropDownList ID="memberID1" AutoPostBack="true" runat="server" Visible="false" OnSelectedIndexChanged="ddlpid1_SelectedIndexChanged">
</asp:DropDownList>
<asp:DropDownList ID="memberID2" AutoPostBack="true" runat="server" Visible="false" OnSelectedIndexChanged="ddlpid2_SelectedIndexChanged">
</asp:DropDownList>
<asp:DropDownList ID="memberID3" AutoPostBack="true" runat="server" Visible="false" OnSelectedIndexChanged="ddlpid3_SelectedIndexChanged" >
</asp:DropDownList>
Update: We can store selected values in view state and retrieve after repopulating the dropdownlists like below:
public partial class WebForm2 : System.Web.UI.Page
{
bool bFlag = true;
protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
{
FillddlLocations();
}
}
//Properties to store selected value in ViewState
protected string MemberID1Selection
{
get
{
if (ViewState["MemberID1Selection"] != null)
return ViewState["MemberID1Selection"].ToString();
return "";
}
set { ViewState["MemberID1Selection"] = value; }
}
protected string MemberID2Selection
{
get
{
if (ViewState["MemberID2Selection"] != null)
return ViewState["MemberID2Selection"].ToString();
return "";
}
set { ViewState["MemberID2Selection"] = value; }
}
protected string MemberID3Selection
{
get
{
if (ViewState["MemberID3Selection"] != null)
return ViewState["MemberID3Selection"].ToString();
return "";
}
set { ViewState["MemberID3Selection"] = value; }
}
protected void FillddlLocations()
{
FillDropdown(memberID1);
FillDropdown(memberID2);
FillDropdown(memberID3);
memberID1.Visible = true;
memberID2.Visible = true;
memberID3.Visible = true;
}
protected void FillDropdown(DropDownList ddl)
{
using (var connAdd = new SqlConnection("Data Source = localhost; Initial Catalog = MajorProject; Integrated Security= SSPI"))
{
connAdd.Open();
var sql = "Select policeid from PoliceAccount where status ='available' and handle ='offcase' and postedto='" + ddllocation.SelectedValue + "'";
using (var cmdAdd = new SqlDataAdapter(sql, connAdd))
{
DataSet ds2 = new DataSet();
cmdAdd.Fill(ds2);
ddl.Items.Clear();
ddl.DataSource = ds2;
ddl.DataTextField = "memberID";
ddl.DataValueField = "memberID";
ddl.DataBind();
ddl.Items.Insert(0, new ListItem("Please select a Member ID", ""));
ddl.SelectedIndex = 0;
}
}
}
protected void IndexChanged(DropDownList ddlChanged, DropDownList ddlToFilter1, DropDownList ddlToFilter2)
{
string removeValue1 = ddlChanged == memberID1 ? MemberID1Selection : (ddlChanged == memberID2 ? MemberID2Selection : MemberID3Selection);
string selValue2 = ddlChanged == memberID1 ? MemberID2Selection : (ddlChanged == memberID2 ? MemberID1Selection : MemberID1Selection);
string selValue3 = ddlChanged == memberID1 ? MemberID3Selection : (ddlChanged == memberID2 ? MemberID3Selection : MemberID2Selection);
bFlag = false;//Prevent fireing the code again while changing the index
if (removeValue1 != "")
{
ListItem item1 = ddlToFilter1.Items.FindByValue(removeValue1);
ddlToFilter1.Items.Remove(item1);
ListItem item2 = ddlToFilter2.Items.FindByValue(removeValue1);
ddlToFilter2.Items.Remove(item2);
}
if (selValue3 != "")
{
ListItem item3 = ddlToFilter1.Items.FindByValue(selValue3);
ddlToFilter1.Items.Remove(item3);
}
if (selValue2 != "")
{
ListItem item4 = ddlToFilter2.Items.FindByValue(selValue2);
ddlToFilter2.Items.Remove(item4);
}
bFlag = false;
ddlToFilter1.SelectedIndex = ddlToFilter1.Items.IndexOf(ddlToFilter1.Items.FindByValue(selValue2));
ddlToFilter2.SelectedIndex = ddlToFilter2.Items.IndexOf(ddlToFilter2.Items.FindByValue(selValue3));
}
protected void ddlpid1_SelectedIndexChanged(object sender, EventArgs e)
{
MemberID1Selection = memberID1.SelectedValue;
if (bFlag)
{
FillDropdown(memberID2);
FillDropdown(memberID3);
IndexChanged(memberID1, memberID2, memberID3);
}
}
protected void ddlpid2_SelectedIndexChanged(object sender, EventArgs e)
{
MemberID2Selection = memberID2.SelectedValue;
if (bFlag)
{
FillDropdown(memberID1);
FillDropdown(memberID3);
IndexChanged(memberID2, memberID1, memberID3);
}
}
protected void ddlpid3_SelectedIndexChanged(object sender, EventArgs e)
{
MemberID3Selection = memberID3.SelectedValue;
if (bFlag)
{
FillDropdown(memberID1);
FillDropdown(memberID2);
IndexChanged(memberID3, memberID1, memberID2);
}
}
}
I have tested the code and it is working for me. Hope it helps!