如何隐藏空的数据绑定下拉列表

问题描述：

我有一个数据绑定DropDownList，我需要一个只显示DropDownList的代码，如果数据库中有值，如果没有值/空DropDownlist则不应该可见。

我尝试了什么：

if（ddlFruits.Items.Count == 1）

{

ddlFruits.Visible = false;

}

else

{

ddlFruits.Visible = true;

}

I have a databound DropDownList and I need a code that will only show the DropDownList if there is a value in the Database, if the there is no value/empty DropDownlist it should not be visible.

What I have tried:

if (ddlFruits.Items.Count == 1)
{
ddlFruits.Visible = false;
}
else
{
ddlFruits.Visible = true;
}

答

所以，基本上你需要处理可见属性。当你从数据库中获取值时，只需检查null和空。

如果不为null且不为空，则 Visible = true ，否则， Visible = false 。

So, basically you need to handle the Visible property. When you get the value from database, just check for null and empty.

If not null and not empty, then Visible = true, else, Visible = false.

而不是检查 DropDownList中的Items ，检查 DropDownList 使用的 DataSource 。例如，如果您使用 DataTable 作为 DataSource ，那么您可以在 Page_Load 事件：

Instead of checking the Items from the DropDownList, check for the DataSource that is used by your DropDownList. For example, if you are using a DataTable as your DataSource then you could do something like this at Page_Load event:

private string GetConnectionString(){
       //calling the connection string that was set up from the web config file
        return ConfigurationManager.ConnectionStrings["DBConnection"].ConnectionString;
}

private void BindDropDownList(){
           DataTable dt = new DataTable();
           using (SqlConnection sqlConn = new SqlConnection(GetConnectionString())){
                string sql = "SELECT Field1, Field2 FROM YourTable WHERE Field3 = @Param1";
                using(SqlCommand sqlCmd = new SqlCommand(sql,sqlConn)){
                    sqlCmd.Parameters.AddWithValue("@Param1", "YourFilterValueHere");
                    sqlConn.Open();
                    using(SqlDataAdapter sqlAdapter = new SqlDataAdapter(sqlCmd))
                    {
                        sqlAdapter.Fill(dt);
                    }
                }
            }

            if (dt.Rows.Count > 0)
            {
                DropDownList1.DataSource =dt;
                DropDownList1.DataTextField = "Field2"; // the items to be displayed in the list items
                DropDownList1.DataValueField = "Field1"; // the id of the items displayed
                DropDownList1.DataBind();
            }
            else
            {
                  DropDownList1.Visible = false;
            }
       
}


protected void Page_Load(object sender, EventArgs e){
        if (!IsPostBack)
            BindDropDownList();
}

如何隐藏空的数据绑定下拉列表

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