text box item not removed - html

Question

i have a 1) Text filed
2) Drop down list
3)List Box
Im write code for Drop down list selected value add the the list box and text filed , i can remove the list box value but cant remove the text filed value, please how to write code remove the same adding value for text filed and list box
<div class="col-sm-3">
<asp:TextBox ID="txtQlt" runat="server" CssClass="form-control" Width="348px" OnTextChanged="txtQlt_TextChanged" ReadOnly="true"></asp:TextBox>
</div><div class="col-md-1" style="margin-left:115px;">
<asp:Label ID="Label4" runat="server" ForeColor="Red" Text="*" ></asp:Label>
</div>
</div>
<br />
<div class="row">
<div class="col-sm-2">
<asp:Label ID="Label6" runat="server" Text="Quality reference" Font-Bold="True" Font-Names="arial, helvetica, sans-serif" Font-Size="13px"></asp:Label>
</div>
<div class="col-sm-3">
<asp:DropDownList ID ="cmbQualityRef" runat ="server" CssClass="form-control" Width="250px" >
</asp:DropDownList>
<asp:ListBox ID="lstValue" runat="server" CssClass="content" Rows="5" ValidationGroup="save"
Width="250" ></asp:ListBox>
</div>
<asp:ImageButton ID="btnAdd" runat="server" CssClass="button" Text="Add" ValidationGroup="add"
OnClick="btnAdd_Click" ImageUrl="~/img/Add.png"/>
<asp:ImageButton ID="btnImageRemove" runat="server" OnClick="btnImageRemove_Click"
ImageUrl="~/img/Remove.png" />
<div class="col-md-1" style="margin-left:16px;">
<asp:Label ID="Label7" runat="server" ForeColor="Red" Text="*" ></asp:Label>
</div>
</div>
Code Behind
protected void btnImageRemove_Click(object sender, ImageClickEventArgs e)
{
try
{
if (lstValue.SelectedItem != null)
{
lstValue.Items.Remove(lstValue.SelectedItem);
}
//lstValue.Items.Remove(lstValue.SelectedItem.Text);
}
catch (Exception)
{
}
}
private void AddToList()
{
if (lstValue.Items.Count > 0)
{
txtQlt.Text = txtQlt.Text + "," + cmbQualityRef.SelectedItem.ToString();
}
else
{
txtQlt.Text = cmbQualityRef.SelectedItem.ToString();
}
ListItem itm = new ListItem();
itm.Value = cmbQualityRef.SelectedValue;
itm.Text = cmbQualityRef.SelectedItem.ToString();
lstValue.Items.Add(itm);
lstValue.Items.Remove("");
}
protected void btnAdd_Click(object sender, EventArgs e)
{
AddToList();
lstValue.Items.Remove("");
}

Answer 1

Based on your question as I understand it, when you are removing the selected item, also set the textbox to empty.
if (lstValue.SelectedItem != null)
{
lstValue.Items.Remove(lstValue.SelectedItem);
txtQlt.Text = txtQlt.Text.Replace(lstValue.SelectedItem.ToString(), "");
}

Answer 2

Finally its working
if (lstValue.SelectedItem != null)
{
txtQlt.Text = txtQlt.Text.Replace(lstValue.SelectedItem.ToString(), "").Trim();
lstValue.Items.Remove(lstValue.SelectedItem);
}