Set UserControl DropDownList selected value in another UserControl TextBox on Button Click in ASP.Net

Hi nauna,

Instead of implementing the click event of inside UserControl you have to implement it inside the content page.

Check the example how to call event of UserControl placed in Content Page with Master Page.

Make sure the event has to be public in user control inorder to to access it everywhere.

HTML

UserControl1

<%@ Control Language="C#" AutoEventWireup="true" CodeFile="WebUserControl1.ascx.cs"
    Inherits="WebUserControl1" %>
<asp:DropDownList ID="ddlEmployees" runat="server">
    <asp:ListItem>Amol Malhotra</asp:ListItem>
    <asp:ListItem>Shambhu Sharma</asp:ListItem>
    <asp:ListItem>Hemant Chopra</asp:ListItem>
    <asp:ListItem>Vishwa M Goswami</asp:ListItem>
    <asp:ListItem>Mohit Kalra</asp:ListItem>
    <asp:ListItem>Abhishek Nigam</asp:ListItem>
    <asp:ListItem>Yogesh Gupta</asp:ListItem>
    <asp:ListItem>Mayank Dhulekar</asp:ListItem>
    <asp:ListItem>Saurabh Mehrotra</asp:ListItem>
    <asp:ListItem>Rakesh Dixit</asp:ListItem>
</asp:DropDownList>
<asp:LinkButton ID="LinkButton1" runat="server" OnClick="LinkButton1_Click">click me</asp:LinkButton>

UserControl2

<%@ Control Language="C#" AutoEventWireup="true" CodeFile="WebUserControl2.ascx.cs"
    Inherits="WebUserControl2" %>
<table style="background-color: skyblue; width: 100%;">
    <tr>
        <td style="height: 10px;">
        </td>
    </tr>
    <tr>
        <td><asp:Button ID="btnDDLValue" runat="server" OnClick="btnDDLValue_Click" Text="Get DropDown Selected Value" /></td>
    </tr>
    <tr>
        <td style="height: 10px;"></td>
    </tr>
    <tr>
        <td>
            Your Selected Employee:<asp:TextBox ID="txtDDLValue" runat="server"></asp:TextBox>
        </td>
    </tr>
</table>

Default Page with Master Page

<%@ Register Src="~/WebUserControl1.ascx" TagPrefix="ctrlA" TagName="WebUserControl1" %>
<%@ Register Src="~/WebUserControl2.ascx" TagPrefix="ctrlA" TagName="WebUserControl2" %>
<asp:Content ID="Content1" ContentPlaceHolderID="head" runat="Server">
</asp:Content>
<asp:Content ID="Content2" ContentPlaceHolderID="ContentPlaceHolder1" runat="Server">
    <table style="background-color: skyblue; width: 100%;">
        <tr>
            <td style="height: 10px;"></td>
        </tr>
        <tr style="padding: 10px;">
            <td>
                Select Employee :
                <ctrlA:WebUserControl1 runat="server" id="WebUserControl1" />
                <ctrlA:WebUserControl2 runat="server" ID="WebUserControl2" />
            </td>
        </tr>
        <tr>
            <td style="height: 10px;"></td>
        </tr>
        <tr>
            <td></td>
        </tr>
    </table>
</asp:Content>

Code

UserControl1

public void LinkButton1_Click(object sender, EventArgs e)
{

}

UserControl2

public void btnDDLValue_Click(object sender, EventArgs e)
{

}

public void assignvalue(string value)
{
    txtDDLValue.Text = value;
}

DefaultPage

Registering click event of user control in Page_Load event.

protected void Page_Load(object sender, EventArgs e)
{
    WebUserControl1 ctrlA = (WebUserControl1)Page.Master.FindControl("ContentPlaceHolder1").FindControl("WebUserControl1");
    WebUserControl2 ctrlB = (WebUserControl2)Page.Master.FindControl("ContentPlaceHolder1").FindControl("WebUserControl2");
    (ctrlA.FindControl("LinkButton1") as LinkButton).Click += LinkButton1_Click;
    (ctrlB.FindControl("btnDDLValue") as Button).Click += btnDDLValue_Click;
}

protected void LinkButton1_Click(object sender, EventArgs e)
{
    WebUserControl1 ctrlA = (WebUserControl1)Page.Master.FindControl("ContentPlaceHolder1").FindControl("WebUserControl1");
    WebUserControl2 ctrlB = (WebUserControl2)Page.Master.FindControl("ContentPlaceHolder1").FindControl("WebUserControl2");
    ctrlB.assignvalue((ctrlA.FindControl("ddlEmployees") as DropDownList).SelectedValue);
    ClientScript.RegisterClientScriptBlock(this.GetType(), "", "alert('User control 1 LinkButton clicked')", true);
}

protected void btnDDLValue_Click(object sender, EventArgs e)
{
    ClientScript.RegisterClientScriptBlock(this.GetType(), "", "alert('User control 2 Button clicked')", true);
}

Screenshot

Default Page without Master Page

<%@ Register Src="~/WebUserControl1.ascx" TagPrefix="ctrlA" TagName="WebUserControl1" %>
<%@ Register Src="~/WebUserControl2.ascx" TagPrefix="ctrlA" TagName="WebUserControl2" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
    <title></title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
        <table style="background-color: skyblue; width: 100%;">
            <tr>
                <td style="height: 10px;"></td>
            </tr>
            <tr style="padding: 10px;">
                <td>
                    Select Employee :
                    <ctrlA:WebUserControl1 runat="server" ID="WebUserControl1" />
                    <ctrlA:WebUserControl2 runat="server" ID="WebUserControl2" />
                </td>
            </tr>
            <tr>
                <td style="height: 10px;"></td>
            </tr>
            <tr>
                <td></td>
            </tr>
        </table>
    </div>
    </form>
</body>
</html>

Code without Master page

protected void Page_Load(object sender, EventArgs e)
{
    WebUserControl1 ctrlA = (WebUserControl1)Page.FindControl("WebUserControl1");
    WebUserControl2 ctrlB = (WebUserControl2)Page.FindControl("WebUserControl2");
    (ctrlA.FindControl("LinkButton1") as LinkButton).Click += LinkButton1_Click;
    (ctrlB.FindControl("btnDDLValue") as Button).Click += btnDDLValue_Click;
}

protected void LinkButton1_Click(object sender, EventArgs e)
{
    WebUserControl1 ctrlA = (WebUserControl1)Page.FindControl("WebUserControl1");
    WebUserControl2 ctrlB = (WebUserControl2)Page.FindControl("WebUserControl2");
    ctrlB.assignvalue((ctrlA.FindControl("ddlEmployees") as DropDownList).SelectedValue);
    ClientScript.RegisterClientScriptBlock(this.GetType(), "", "alert('User control 1 LinkButton clicked')", true);
}

protected void btnDDLValue_Click(object sender, EventArgs e)
{
    ClientScript.RegisterClientScriptBlock(this.GetType(), "", "alert('User control 2 Button clicked')", true);
}

Screenshot