Question

如何停止在DropDownLists中重复数据？我找不到任何有来自sql的非重复值的DropDownlists的好例子？我试着让select语句说明了区别。

这是我正在使用的代码：

protected void Page_Load(object sender, EventArgs e)
{
    Label1.Text = (string)Session["name"];

    if (!IsPostBack)
    {
        DropDownList1.AppendDataBoundItems = true;
        DropDownList2.AppendDataBoundItems = true;
        DropDownList3.AppendDataBoundItems = true;
        DropDownList4.AppendDataBoundItems = true;
        String strConnString = ConfigurationManager
            .ConnectionStrings["connectionString"].ConnectionString;
        String strQuery = "select distinct * from dbo.Vehiclemain WHERE ISENABLED = 'YES'";
        SqlConnection con = new SqlConnection(strConnString);
        SqlCommand cmd = new SqlCommand();
        cmd.CommandType = CommandType.Text;
        cmd.CommandText = strQuery;
        cmd.Connection = con;
        try
        {
            con.Open();
            DropDownList1.DataSource = cmd.ExecuteReader();
            DropDownList1.DataTextField = "Year";
            DropDownList1.DataValueField = "ID";
            DropDownList1.DataBind();
            con.Close();
            con.Open();
            DropDownList2.DataSource = cmd.ExecuteReader();
            DropDownList2.DataTextField = "Make";
            DropDownList2.DataValueField = "ID";
            DropDownList2.DataBind();
            con.Close();
            con.Open();
            DropDownList3.DataSource = cmd.ExecuteReader();
            DropDownList3.DataTextField = "Model";
            DropDownList3.DataValueField = "ID";
            DropDownList3.DataBind();
            con.Close();
            con.Open();
            DropDownList4.DataSource = cmd.ExecuteReader();
            DropDownList4.DataTextField = "Submodel";
            DropDownList4.DataValueField = "ID";
            DropDownList4.DataBind();
            con.Close();
        }
        catch (Exception ex)
        {
            throw ex;
        }
        finally
        {
            con.Close();
            con.Dispose();
        }
    }

Answer 1

您正在使用单个查询来填充所有下拉列表。尝试创建4个选择的状态，并将不同的列应用于相应的列。对于ex Make下拉将在查询中具有不同的Make。

Answer 2

看起来您想要根据第一个下拉菜单更改下拉菜单。如果是这种情况，那么您也希望将下拉列表恢复为自动提交。每当有人更改年份时，将根据年份填写制作。每当有人更改make时，都会根据make填充模型。每当有人更改模型时，将根据模型填充子模型。在我们构建信息时，sQL查询将被搭建......

以下代码尚未经过测试。

<asp:DropDownList ID="ddlYearObj" runat="server" AutoPostBack="True" OnSelectedIndexChanged="ddlObj_SelectedIndexChanged" ></asp:DropDownList>
<asp:DropDownList ID="ddlMakeObj" runat="server" AutoPostBack="True" OnSelectedIndexChanged="ddlMakeObj_SelectedIndexChanged" Visible="false"></asp:DropDownList>
<asp:DropDownList ID="ddlModelObj" runat="server" AutoPostBack="True" OnSelectedIndexChanged="ddlModelObj_SelectedIndexChanged" Visible="false"></asp:DropDownList>
<asp:DropDownList ID="ddlSubmodelObj" runat="server" Visible="false"></asp:DropDownList>

protected void Page_Load(object sender, EventArgs e)
{
    Label1.Text = (string)Session["name"];

    if (!IsPostBack)
    {
        String strConnString = ConfigurationManager
            .ConnectionStrings["connectionString"].ConnectionString;
        String strQuery = "select distinct Year from dbo.Vehiclemain WHERE ISENABLED = 'YES'";
        SqlConnection con = new SqlConnection(strConnString);
        SqlCommand cmd = new SqlCommand();
        cmd.CommandType = CommandType.Text;
        cmd.CommandText = strQuery;
        cmd.Connection = con;
        try
        {
            con.Open();
            ddlYearObj.DataSource = cmd.ExecuteReader();
            ddlYearObj.DataTextField = "Year";
            ddlYearObj.DataValueField = "Year";
            ddlYearObj.DataBind();
            con.Close();
        }
        catch (Exception ex)
        {
            throw ex;
        }
        finally
        {
            con.Close();
            con.Dispose();
        }

        //Visible!? -- All invisible until something is chosen
        ddlMakeObj.Visible = false;
        ddlModelObj.Visible = false;
        ddlSubmodelObj.Visible = false;
    }
    protected void ddlYearObj_SelectedIndexChanged(object sender, EventArgs e)
    {
        String strConnString = ConfigurationManager
            .ConnectionStrings["connectionString"].ConnectionString;
        String strQuery = "select distinct Make from dbo.Vehiclemain WHERE ISENABLED = 'YES' AND YEAR = "+ ddlYearObj.Value;
        SqlConnection con = new SqlConnection(strConnString);
        SqlCommand cmd = new SqlCommand();
        cmd.CommandType = CommandType.Text;
        cmd.CommandText = strQuery;
        cmd.Connection = con;
        try
        {
            con.Open();
            ddlMakeObj.DataSource = cmd.ExecuteReader();
            ddlMakeObj.DataTextField = "Make";
            ddlMakeObj.DataValueField = "Make";
            ddlMakeObj.DataBind();
            con.Close();
        }
        catch (Exception ex)
        {
            throw ex;
        }
        finally
        {
            con.Close();
            con.Dispose();
        }

        //Visible!
        ddlMakeObj.Visible = true;
        ddlModelObj.Visible = false;
        ddlSubmodelObj.Visible = false;
    }
    protected void ddlMakeObj_SelectedIndexChanged(object sender, EventArgs e)
    {
        String strConnString = ConfigurationManager
            .ConnectionStrings["connectionString"].ConnectionString;
        String strQuery = "select distinct modelfrom dbo.Vehiclemain WHERE ISENABLED = 'YES' AND YEAR = "+ ddlYearObj.Value;
        SqlConnection con = new SqlConnection(strConnString);
        SqlCommand cmd = new SqlCommand();
        cmd.CommandType = CommandType.Text;
        cmd.CommandText = strQuery;
        cmd.Connection = con;
        try
        {
            con.Open();
            ddlModelObj.DataSource = cmd.ExecuteReader();
            ddlModelObj.DataTextField = "Model";
            ddlModelObj.DataValueField = "Model";
            ddlModelObj.DataBind();
            con.Close();
        }
        catch (Exception ex)
        {
            throw ex;
        }
        finally
        {
            con.Close();
            con.Dispose();
        }

        //Visible!
        ddlMakeObj.Visible = true;
        ddlModelObj.Visible = true;
        ddlSubmodelObj.Visible = false;
    }
    protected void ddlModelObj_SelectedIndexChanged(object sender, EventArgs e)
    {
        String strConnString = ConfigurationManager
            .ConnectionStrings["connectionString"].ConnectionString;
        String strQuery = "select distinct Submodelfrom dbo.Vehiclemain WHERE ISENABLED = 'YES' AND YEAR = "+ ddlYearObj.Value + " AND Model = '" + ddlModelObj.Value + "'";
        SqlConnection con = new SqlConnection(strConnString);
        SqlCommand cmd = new SqlCommand();
        cmd.CommandType = CommandType.Text;
        cmd.CommandText = strQuery;
        cmd.Connection = con;
        try
        {
            con.Open();
            ddlSubmodelObj.DataSource = cmd.ExecuteReader();
            ddlSubmodelObj.DataTextField = "Submodel";
            ddlSubmodelObj.DataValueField = "ID";
            ddlSubmodelObj.DataBind();
            con.Close();
        }
        catch (Exception ex)
        {
            throw ex;
        }
        finally
        {
            con.Close();
            con.Dispose();
        }

        //Visible!
        ddlMakeObj.Visible = true;
        ddlModelObj.Visible = false;
        ddlSubmodelObj.Visible = true;
    }

下拉列表没有重复数据值

2 个答案: