While doing pagination and sorting web grid become empty

  @{
        var grid = new WebGrid(Model, ajaxUpdateContainerId: "ajaxgrid", rowsPerPage: 20, canPage: true, canSort: true, ajaxUpdateCallback: "GetstatusbyAppraisalid");

        IEnumerable<webgridcolumn> cols =
            new List<webgridcolumn> {

                    new WebGridColumn{
                        ColumnName="empid",
                        Header="emp ID",

                        CanSort = true,Style= "colour:black !important",
                        Format = @<text>
        <span class="display"><label id="lblKraId">@item.empid</label></span>

                        </text>
                    },
                    new WebGridColumn{
                         ColumnName="emp",
                        Header="EmployeeID",
                        Format = @<text>

        <span class="display"><label id="lblName">@item.EmployeeId</label></span>


                        </text>
                    },
                    new WebGridColumn{
                        ColumnName="",
                        Header="Empname",
                        Format = @<text>
        <span class="display"><label id="lblWeightage">@item.EmployeeName</label></span>

                        </text>
                    },
                    new WebGridColumn{
                        ColumnName="Grade",
                        Header="Grade",

                        Format = @<text>
        <span class="display"><label id="lblEmail">@item.Grade</label></span>



                        </text>
                    },
                    new WebGridColumn{
                        ColumnName="Position",
                        Header="Position",
                            CanSort = true,Style= "colour:black !important",
                        Format = @<text>
        <span class="display"><label id="lblpos">@item.Position</label></span>


                        </text>
                    },
                    new WebGridColumn{
                        ColumnName="status",
                        Header="Status",
                        Format = @<text>

        <span class="display"><label id="lblStatus">@item.AppraisalStatus</label></span>

                        </text>
                    },
                    new WebGridColumn{
                        Header="Action",
                        Format = @<text>
        <input type="radio" />
                        </text>
                    },
                };
    }
</webgridcolumn></webgridcolumn></div>

@grid.GetHtml(columns: cols, rowStyle: "oddRowStyle", alternatingRowStyle: "evenRowStyle"
    , tableStyle: "gridTable", selectedRowStyle: "gridAltRow", htmlAttributes: new { id = "ajaxgrid" })