aspGridView and DropDownList.

Question

User1266884534 posted

Hello Folks,
I have a form that has aspGridView control on it. The control is displayed when a search is performed on the page. The issue I am facing is with a <g class="gr_ gr_393 gr-alert gr_spell gr_inline_cards gr_run_anim ContextualSpelling ins-del multiReplace" id="393" data-gr-id="393">dropdownlist</g> on this control. The dropdown list is getting populated with all the values, but I am not able to display the <g class="gr_ gr_718 gr-alert gr_spell gr_inline_cards gr_run_anim ContextualSpelling ins-del multiReplace" id="718" data-gr-id="718">selectedValue</g>.

I have the code to populate the <g class="gr_ gr_808 gr-alert gr_spell gr_inline_cards gr_run_anim ContextualSpelling" id="808" data-gr-id="808">dropdownlist</g> control in the RowDataBound event of the <g class="gr_ gr_823 gr-alert gr_spell gr_inline_cards gr_run_anim ContextualSpelling ins-del multiReplace" id="823" data-gr-id="823">gridview</g> control. Here is the snippet of code.

The <g class="gr_ gr_897 gr-alert gr_spell gr_inline_cards gr_run_anim ContextualSpelling ins-del multiReplace" id="897" data-gr-id="897">selectedValue</g> property assignment fails with the following message --> 

'dr["Id"].ToString()' threw an exception of type 'System.NullReferenceException'

  protected void gridResults_RowDataBound(object sender, GridViewRowEventArgs e)
        {
            if (e.Row.RowType == DataControlRowType.DataRow)
            {

                    var ddlAccountType = DropDownList)e.Row.FindControl("dlAccountType");
                    ddlAccountType.DataSource = DataLayer.GetAllAccountTypes();
                    ddlAccountType.DataTextField = "Type";
                    ddlAccountType.DataValueField = "Id";
                    ddlAccountType.DataBind();
                    DataRowView dr = e.Row.DataItem as DataRowView;
                    ddlAccountType.SelectedValue = dr["Id"].ToString();
   }
        }

Answer 1

User1266884534 posted

So I had to change part of the code in order to assign the DataItem value correctly. Here is the updated code.

                    var ddlAccountType = (DropDownList)e.Row.FindControl("dlAccountType");
                    ddlAccountType.DataSource = DataLayer.GetAllAccountTypes();
                    ddlAccountType.DataTextField = "Type";
                    ddlAccountType.DataValueField = "Id";
                    ddlAccountType.DataBind();
                    var glaccountTypeId = Convert.ToInt32(DataBinder.Eval(e.Row.DataItem, "Id"));
                    ddlAccountType.Items.FindByValue(glaccountTypeId.ToString()).Selected = true;

Answer 2

User1535942433 posted

Hi learning_to_code,

Accroding to your description and codes,I suggest you could debug to check wheather  dr["Id"] is null.What is your grdiview aspx page and what is your dropdownlist data?

Do you have field of Id in dropdownlist data?I create a demo.

More details,you could refer to below codes:

ASPX:

 <div>
            <asp:GridView ID="GridView1" runat="server" OnRowDataBound="GridView1_RowDataBound" AutoGenerateColumns="False">
                <Columns>
                    <asp:TemplateField HeaderText="Id">
                        <ItemTemplate>
                            <asp:Label runat="server" Text='<%# Eval("Id") %>'></asp:Label>
                        </ItemTemplate>
                    </asp:TemplateField>
                    <asp:TemplateField HeaderText="Name">
                        <ItemTemplate>
                            <asp:Label runat="server" Text='<%# Eval("Name") %>'></asp:Label>
                        </ItemTemplate>
                    </asp:TemplateField>
                    <asp:TemplateField HeaderText="Value">
                        <ItemTemplate>
                            <asp:Label runat="server" Text='<%# Eval("Value") %>'></asp:Label>
                        </ItemTemplate>
                    </asp:TemplateField>
                    <asp:TemplateField HeaderText="ddl">
                        <ItemTemplate>
                           <asp:DropDownList runat="server" ID="dlAccountType"></asp:DropDownList>
                        </ItemTemplate>
                    </asp:TemplateField>
                </Columns>
            </asp:GridView>
        </div>

Code-behind:

protected void Page_Load(object sender, EventArgs e)
        {
            if (!IsPostBack)
            {
                bind();
            }
        }
        protected void bind()
        {
            string str, strSql;
            str = System.Configuration.ConfigurationManager.ConnectionStrings["aspnet-TestApplicationWithDatabase-20190820030542"].ConnectionString;
            SqlConnection conn = new SqlConnection(str);
            strSql = "select * from gv";
            SqlDataAdapter da = new SqlDataAdapter(strSql, str);
            DataSet ds = new DataSet();
            da.Fill(ds, "gv");
            GridView1.DataSource = ds.Tables[0].DefaultView;
            GridView1.DataBind();
            conn.Close();
        }

        protected void GridView1_RowDataBound(object sender, GridViewRowEventArgs e)
        {
            if (e.Row.RowType == DataControlRowType.DataRow)
            {
                string query = "select Id,Type from gv";
                SqlConnection sqlConn = new SqlConnection(System.Configuration.ConfigurationManager.ConnectionStrings["aspnet-TestApplicationWithDatabase-20190820030542"].ConnectionString);
                sqlConn.Open();
                SqlDataAdapter da = new SqlDataAdapter();
                da.SelectCommand = new SqlCommand(query, sqlConn);
                DataTable dt = new DataTable();
                da.Fill(dt);
                sqlConn.Close();


                var ddlAccountType = (DropDownList)e.Row.FindControl("dlAccountType");
                ddlAccountType.DataSource = dt;
                ddlAccountType.DataTextField = "Type";
                ddlAccountType.DataValueField = "Id";
                ddlAccountType.DataBind();
                DataRowView dr = e.Row.DataItem as DataRowView;
                ddlAccountType.SelectedValue = dr["Id"].ToString();
            }
        }

Result:

Best regards,

Yijing Sun