repeater 页面截取控制字符长度,该如何处理

repeater 页面截取控制字符长度
后台：
  public string GetString(string str, int length)
  {
  if (str.Length > length)
  return str = str.Substring(0, length);
  else
  return str;
  }


前台：
 <asp:Repeater runat="server" ID="repeater_list" OnItemDataBound="repeater_list_ItemDataBound">
  <ItemTemplate>
  <tr onmouseover='setcolorup(this);' onmouseout='setcolordown(this);' onclick="rowcheck(this)"
  ondblclick="document.location.href='fo01view.aspx?TeachId=<%#Eval("TECHACCEPT_ID")%>';">
  <td>
  <%#Eval("IDEN_STATE_NAME")%>
  </td>
  <td>
  <%#Eval("FINACE_STATE_NAME")%>
  </td>
  <td>
  <%#Eval("TECHACCEPT_NO")%>
  </td>
  <td>
  <%#Eval("FM_CITY")%>
  </td>
  <td>
  <%#Eval("TECHACCEPT_TYPE_NAME")%>
  </td>
  <td>
  <%#Eval("FM_TYPE")%>
  </td>
  <td>
  <%#Eval("FM_CLASS")%>
  </td>
  <td>
  <%#GetString(Eval("ARC_CONCLUSION").ToString(),5)%> 
  </td>
  <td>
  <%#Eval("ARC_NAME")%>
  </td>
  <td>
  <%#Eval("IDENT_MAIN")%>
  </td>
  <td>
  <%#Eval("ARC_ASS_NAME")%>
  </td>
  <td>
  <asp:LinkButton ID="LinkBtnDel" OnClientClick="return confirm('确定删除？')" OnClick="linkBtn_Del_Click"
  runat="server">删除</asp:LinkButton>
  </td>
  </tr>
  </ItemTemplate>
  </asp:Repeater>


<%#GetString(Eval("ARC_CONCLUSION").ToString(),5)%> 
提示未将对象引用到实例

------解决方案--------------------------------------------------------
<%=GetString(Eval("ARC_CONCLUSION").ToString(),5)%>
用=号
------解决方案--------------------------------------------------------

C# code

 public string GetString(string str, int length)            {                string returnStr = string.Empty;                if (!string.IsNullOrEmpty(str))                {                    if (str.Length > length)                        returnStr = str.Substring(0, length);                }                return returnStr;            }
------解决方案--------------------------------------------------------