When user clicks the “select/deselect all” checkbox in the column header, the OnCheckBoxClick client-side event is invoked. We can utilize this behavior in order to check/uncheck rows that are enabled.

function WebGrid1_OnCheckBoxClick(controlId, tblName, colName, checkboxValue, originalCheckBoxValue) {
    var WebGrid1 = ISGetObject(controlId);
    var rowIndex = WebGrid1.CheckedRowContext.rowIndex;

    if (!WebGrid1.RootTable.GetRow(rowIndex).ForceNoEdit) {
        window.setTimeout(
    function () {
        WebGrid1.RootTable.GetRow(rowIndex).Uncheck();
    }, 1);
    }

    return true;
}

The snippet code as shown in above uses “if” to check whether the ForceNoEdit property of current row is true or not. If true (disabled records), then uncheck the checkbox by invoking Uncheck() method.

Hope this helps.