我在网格视图中有2个下拉列表。选择第一个（EqpCatDDL）将确定将填充第二个（DescripDDL）的值。
但是，每次单击Add New Row按钮时，DescripDDL下拉列表都会清除。我不知道为什么会这样。以下是代码：
ASPX：
<asp:ScriptManager ID="ScriptManager1" runat="server"></asp:ScriptManager>
<asp:UpdatePanel runat="server">
<ContentTemplate>
<asp:GridView ID="Gridview1" runat="server" ShowFooter="True" AutoGenerateColumns="False"
OnRowDataBound="Gridview1_RowDataBound">
<Columns>
<asp:BoundField DataField="S/N" HeaderText="S/N" />
<asp:TemplateField HeaderText="Item Name">
<ItemTemplate>
<asp:DropDownList ID="EqpCatDDL" runat="server" AutoPostBack="true" OnSelectedIndexChanged="EqpCatDDL_SelectedIndexChanged">
</asp:DropDownList>
</ItemTemplate>
</asp:TemplateField>
<asp:TemplateField HeaderText="Description">
<ItemTemplate>
<asp:DropDownList ID="DescripDDL" runat="server" AutoPostBack="true">
</asp:DropDownList>
</ItemTemplate>
</asp:TemplateField>
<asp:TemplateField HeaderText="Quantity">
<ItemTemplate>
<asp:TextBox ID="TextBox3" runat="server"></asp:TextBox>
</ItemTemplate>
</asp:TemplateField>
<asp:TemplateField HeaderText="Remarks">
<ItemTemplate>
<asp:TextBox ID="TextBox4" runat="server"></asp:TextBox>
</ItemTemplate>
<FooterStyle HorizontalAlign="Right" />
<FooterTemplate>
<contenttemplate>
<asp:Button ID="ButtonAdd" onclick="ButtonAdd_Click" runat="server" Text="Add New Row" />
</contenttemplate>
</FooterTemplate>
</asp:TemplateField>
</Columns>
</asp:GridView>
</ContentTemplate>
</asp:UpdatePanel>
C＃：
protected void Page_Load(object sender, EventArgs e)
{
if (!Page.IsPostBack)
{
SetInitialRow(); //create a datatable to bind to GridView
}
}
private void SetInitialRow()
{
DataTable dt = new DataTable();
DataRow dr = null;
dt.Columns.Add(new DataColumn("S/N", typeof(string)));
dt.Columns.Add(new DataColumn("Column1", typeof(string)));
dt.Columns.Add(new DataColumn("Column2", typeof(string)));
dt.Columns.Add(new DataColumn("Column3", typeof(string)));
dt.Columns.Add(new DataColumn("Column4", typeof(string)));
dr = dt.NewRow();
dr["S/N"] = 1;
dr["Column1"] = string.Empty;
dr["Column2"] = string.Empty;
dr["Column3"] = string.Empty;
dr["Column4"] = string.Empty;
dt.Rows.Add(dr);
//Store the DataTable in ViewState
ViewState["CurrentTable"] = dt;
Gridview1.DataSource = dt;
Gridview1.DataBind();
}
protected void ButtonAdd_Click(object sender, EventArgs e)
{
AddNewRowToGrid();
GridViewRow row = (GridViewRow)((sender as Button).NamingContainer);
Button btn = row.FindControl("ButtonAdd") as Button;
ScriptManager.GetCurrent(this).RegisterAsyncPostBackControl(btn);
}
private void AddNewRowToGrid()
{
int rowIndex = 0;
if (ViewState["CurrentTable"] != null)
{
DataTable dtCurrentTable = (DataTable)ViewState["CurrentTable"];
DataRow drCurrentRow = null;
if (dtCurrentTable.Rows.Count > 0)
{
//extract the TextBox values
for (int i = 1; i <= dtCurrentTable.Rows.Count; i++)
{
//Locate controls in GridView
DropDownList ddl1 = (DropDownList)Gridview1.Rows[rowIndex].Cells[1].FindControl("EqpCatDDL");
DropDownList ddl2 = (DropDownList)Gridview1.Rows[rowIndex].Cells[2].FindControl("DescripDDL");
TextBox box3 = (TextBox)Gridview1.Rows[rowIndex].Cells[3].FindControl("TextBox3");
TextBox box4 = (TextBox)Gridview1.Rows[rowIndex].Cells[4].FindControl("TextBox4");
//Save control values into DataTable
drCurrentRow = dtCurrentTable.NewRow();
drCurrentRow["S/N"] = i + 1;
drCurrentRow["Column1"] = ddl1.SelectedValue.ToString();
drCurrentRow["Column2"] = ddl2.SelectedValue.ToString();
drCurrentRow["Column3"] = box3.Text;
drCurrentRow["Column4"] = box4.Text;
dtCurrentTable.Rows[rowIndex]["Column1"] = ddl1.SelectedValue.ToString();
dtCurrentTable.Rows[rowIndex]["Column2"] = ddl2.SelectedValue.ToString();
dtCurrentTable.Rows[rowIndex]["Column3"] = box3.Text;
dtCurrentTable.Rows[rowIndex]["Column4"] = box4.Text;
rowIndex++;
}
//add new row to DataTable
dtCurrentTable.Rows.Add(drCurrentRow);
//Store the current data to ViewState
ViewState["CurrentTable"] = dtCurrentTable;
//Rebind the Grid with the current data
Gridview1.DataSource = dtCurrentTable;
Gridview1.DataBind();
}
}
else
{
Response.Write("ViewState is null");
}
SetPreviousData(); //Set Previous Data from DataTable to GridView on Postbacks from Add New Row button click
}
private void SetPreviousData()
{
int rowIndex = 0;
if (ViewState["CurrentTable"] != null)
{
DataTable dt = (DataTable)ViewState["CurrentTable"];
if (dt.Rows.Count > 0)
{
for (int i = 0; i < (dt.Rows.Count-1); i++)
{
DropDownList ddl1 = (DropDownList)Gridview1.Rows[rowIndex].Cells[1].FindControl("EqpCatDDL");
DropDownList ddl2 = (DropDownList)Gridview1.Rows[rowIndex].Cells[2].FindControl("DescripDDL");
TextBox box3 = (TextBox)Gridview1.Rows[rowIndex].Cells[3].FindControl("TextBox3");
TextBox box4 = (TextBox)Gridview1.Rows[rowIndex].Cells[4].FindControl("TextBox4");
ddl1.Text = dt.Rows[i]["Column1"].ToString();
ddl2.Text = dt.Rows[i]["Column2"].ToString();
box3.Text = dt.Rows[i]["Column3"].ToString();
box4.Text = dt.Rows[i]["Column4"].ToString();
rowIndex++;
}
}
}
}
//Populate Item Name dropdownlist from EqpCat column in EqpCategory table
protected void Gridview1_RowDataBound(object sender, GridViewRowEventArgs e)
{
if (e.Row.RowType == DataControlRowType.DataRow)
{
string connString = ConfigurationManager.ConnectionStrings["MyDbConn"].ConnectionString;
SqlConnection connection = new SqlConnection(connString);
//Find the DropDownList in the Row
DropDownList EqpCatDDL = (e.Row.FindControl("EqpCatDDL") as DropDownList);
SqlCommand cmd1 = new SqlCommand("SELECT DISTINCT EqpCat FROM EqpCategory", connection);
cmd1.Connection.Open();
SqlDataReader ddlValues1;
ddlValues1 = cmd1.ExecuteReader();
EqpCatDDL.DataSource = ddlValues1;
EqpCatDDL.DataTextField = "EqpCat";
EqpCatDDL.DataValueField = "EqpCat";
EqpCatDDL.DataBind();
cmd1.Connection.Close();
cmd1.Connection.Dispose();
//Add Default Item in the DropDownList
EqpCatDDL.Items.Insert(0, new ListItem("--Select--"));
}
}
//Populate Description dropdownlist based on selected value of Item Name dropdownlist
protected void EqpCatDDL_SelectedIndexChanged(object sender, EventArgs e)
{
string connString = ConfigurationManager.ConnectionStrings["MyDbConn"].ConnectionString;
SqlConnection connection = new SqlConnection(connString);
GridViewRow gvr = (GridViewRow)((DropDownList)sender).Parent.Parent;
DropDownList EqpCatDDL = gvr.FindControl("EqpCatDDL") as DropDownList;
DropDownList DescripDDL = gvr.FindControl("DescripDDL") as DropDownList;
string cate = EqpCatDDL.SelectedValue.ToString();
SqlCommand cmd2 = new SqlCommand("SELECT Description FROM EqpCategory WHERE EqpCat = '" + cate + "'", connection);
cmd2.Connection.Open();
SqlDataReader ddlValues2;
ddlValues2 = cmd2.ExecuteReader();
DescripDDL.DataSource = ddlValues2;
DescripDDL.DataTextField = "Description";
DescripDDL.DataValueField = "Description";
DescripDDL.DataBind();
cmd2.Connection.Close();
cmd2.Connection.Dispose();
//Add Default Item in the DropDownList
DescripDDL.Items.Insert(0, new ListItem("--Select--"));
}
我目前正在使用：带有SSMS 2008的Visual Studio 2010
答案 0 :(得分：2)
只需修改您的SetPreviousData函数
private void SetPreviousData()
{
int rowIndex = 0;
if (ViewState["CurrentTable"] != null)
{
DataTable dt = (DataTable)ViewState["CurrentTable"];
if (dt.Rows.Count > 0)
{
for (int i = 0; i < (dt.Rows.Count - 1); i++)
{
DropDownList ddl1 = (DropDownList)Gridview1.Rows[rowIndex].Cells[1].FindControl("EqpCatDDL");
DropDownList ddl2 = (DropDownList)Gridview1.Rows[rowIndex].Cells[2].FindControl("DescripDDL");
TextBox box3 = (TextBox)Gridview1.Rows[rowIndex].Cells[3].FindControl("TextBox3");
TextBox box4 = (TextBox)Gridview1.Rows[rowIndex].Cells[4].FindControl("TextBox4");
ddl1.SelectedValue = dt.Rows[i]["Column1"].ToString();
string connString = ConfigurationManager.ConnectionStrings["MyDbConn"].ConnectionString;
SqlConnection connection = new SqlConnection(connString);
SqlCommand cmd2 = new SqlCommand(""SELECT Description FROM EqpCategory WHERE EqpCat = '" + Convert.ToInt32(ddl1.SelectedValue) + "'", connection);
cmd2.Connection.Open();
SqlDataReader ddlValues2;
ddlValues2 = cmd2.ExecuteReader();
ddl2.DataTextField = "Description";
ddl2.DataValueField = "Description";
ddl2.DataSource = ddlValues2;
ddl2.DataBind();
cmd2.Connection.Close();
cmd2.Connection.Dispose();
ddl2.SelectedValue = dt.Rows[i]["Column2"].ToString();
box3.Text = dt.Rows[i]["Column3"].ToString();
box4.Text = dt.Rows[i]["Column4"].ToString();
rowIndex++;
}
}
}
}
答案 1 :(得分：0)
使用SelectedValue（https://msdn.microsoft.com/en-us/library/system.web.ui.webcontrols.listcontrol.selectedvalue(v=vs.110).aspx）代替text来设置所选项目。
例如：
ddl1.SelectedValue = dt.Rows[i]["Column1"].ToString();
ddl2.SelectedValue = dt.Rows[i]["Column2"].ToString();