截断RadGrid列中的文本

Question

using Telerik RadGrid* in a LINQ context, with ASP.NET/C#, how to truncate text to a maximum length when displaying in columns? By maximum, I mean if original string's length is shorter than the specified maximum length, no errors will raise.

I have seen many examples of this on the net, but it seems that the Container.DataItem used to achieve this is different when using LINQ. Sometimes we see DataItem as a method, sometimes not. Examples are usually using a DataSet .

Here's an example found ( source ) :

<asp:TemplateField HeaderText="Description">
  <ItemTemplate>
    <%# ValidateString(Container.DataItem("Description")) %>
  </ItemTemplate>
</asp:TemplateField>

And codebehind:

protected string ValidateString(object String)
{
  if ((String.ToString().Length > 50))
  {
    return String.ToString().Substring(0, 50) + "...";
  }
  else
  {
    return String.ToString();
  }
}

Thank you for the help.

(*) Or a normal GridView, supposed to be compatible.

Answer 1

I would hook into the OnItemDataBound event and perform this in your code behind. Cast the data item as your custom object and query the property, something like the following (typing some from memory):

protected void RadGrid1_ItemDataBound(object sender, Telerik.Web.UI.GridItemEventArgs e)
{
     if (e.Item is GridDataItem)
     {
          GridDataItem dataBoundItem = e.Item as GridDataItem;
          CustomObject o = e.Item.DataItem as CustomObject;

          if(o.Description.Length > 50)
          {
               dataBoundItem["Description"].Text = o.Description.Substring(0, 47) + "..."
          }
      }
}

Alternatively if you want to stick with the method you are using try the following in your aspx

<telerik:GridTemplateColumn>
     <ItemTemplate>
          <%# ValidateString(Eval("Description").ToString()) %>
     </ItemTemplate>
</telerik:GridTemplateColumn>

Answer 2

The idea of rrrr of using ItemDataBound event was a good lead. But, by using a custom query with inner joins for populating my grid, I can't use the CustomObject property. I've used the dataBoundItem["ColumnName"] by modifying directly its text. In fact, the solution was simple!

Here's an example :

protected void RadGrid1_ItemDataBound(object sender, Telerik.Web.UI.GridItemEventArgs e)
{
    if (e.Item is GridDataItem)
    {
        GridDataItem dataBoundItem = e.Item as GridDataItem;
        if (dataBoundItem["ColumnName"].Text.Length > 100)
        {
            dataBoundItem["ColumnName"].Text = dataBoundItem["ColumnName"].Text.Substring(0, 100) + "...";
        }
    }
}

Thanks to rrrr by the way!

Answer 3

Your codes are okay. Just change "Container.DataItem" to "Eval". And keep everything as it is. Then try it. I hope it will work... All the bet

Existing: <%# ValidateString(Container.DataItem("Description")) %>

Changes: <%# ValidateString(Eval("Description")) %>

Answer 4

Using a converter also works for this.

<UserControl.Resources>
    <myConverters:SubStringConverter x:Key="First50CharactersConverter" Length="50" ShowEllipse="True" />
</UserControl.Resources>
...
<telerik:GridViewDataColumn DataMemberBinding="{Binding Comments, Converter={StaticResource First50CharactersConverter}}" Header="Comments">

The converter substring class:

    /// <summary> Mimics the behavior of string.substring for use in XAML </summary>
public class SubStringConverter : IValueConverter
{
    /// <summary> the zero-based starting character position </summary>
    public int StartIndex { get; set; }

    /// <summary> The number of characters in the substring </summary>
    public int Length { get; set; }

    /// <summary> shows "..." if value was truncated after StartIndex</summary>
    public bool ShowEllipse { get; set; }

    public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        string valueString = value as string;
        if (string.IsNullOrWhiteSpace(valueString) == false)
        {
            if (Length > 0 && Length < (valueString.Length + StartIndex))
            {
                if (ShowEllipse)
                    return valueString.Substring(StartIndex, Length - 3) + "...";
                else
                    return valueString.Substring(StartIndex, Length);
            }
            else if (StartIndex < valueString.Length)
                return valueString.Substring(StartIndex);
            else
                return ""; //because startIndex must be past the length of the string
        }
        else
        {
            return value;
        }
    }

    public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        throw new NotImplementedException();
    }
}