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  • 拼linq 时网上整理的一个类

    public static class DynamicLinqExpressions
    {
    public static Expression<Func<T, bool>> True<T>() { return f => true; }
    public static Expression<Func<T, bool>> False<T>() { return f => false; }

    public static Expression<Func<T, bool>> Or<T>(this Expression<Func<T, bool>> expr1,
    Expression<Func<T, bool>> expr2)
    {
    var invokedExpr = Expression.Invoke(expr2, expr1.Parameters.Cast<Expression>());
    return Expression.Lambda<Func<T, bool>>
    (Expression.Or(expr1.Body, invokedExpr), expr1.Parameters);
    }

    public static Expression<Func<T, bool>> And<T>(this Expression<Func<T, bool>> expr1,
    Expression<Func<T, bool>> expr2)
    {
    var invokedExpr = Expression.Invoke(expr2, expr1.Parameters.Cast<Expression>());
    return Expression.Lambda<Func<T, bool>>
    (Expression.And(expr1.Body, invokedExpr), expr1.Parameters);
    }
    }

    用法:

    Expression<Func<DataRow, bool>> expressionResult = DynamicLinqExpressions.True<DataRow>();
    if (!string.IsNullOrEmpty(staffName))
    {
    expressionResult.And(res => res.Field<string>("StaffName").Contains(staffName));
    }
    if (!string.IsNullOrEmpty(staffCode))
    {
    expressionResult.And(res => res.Field<string>("StaffCode")==staffCode);
    }
    if (!string.IsNullOrEmpty(staffAllPing))
    {
    expressionResult.And(res => res.Field<string>("StaffAllPing").Contains(staffAllPing));
    }
    if (!string.IsNullOrEmpty(staffShortPing))
    {
    expressionResult.And(res => res.Field<string>("StaffShortPing").Contains(staffShortPing));
    }
    if (!string.IsNullOrEmpty(selTopCompany) && selTopCompany!="-1")
    {
    expressionResult.And(res => res.Field<string>("CompanyUniqueCode") == selTopCompany);
    }
    if (!string.IsNullOrEmpty(selTopDepartment) && selTopDepartment!="-1")
    {
    expressionResult.And(res => res.Field<string>("DeptUniqueCode") == selTopDepartment);
    }
    if (!string.IsNullOrEmpty(selTopQuarter) && selTopQuarter!="-1")
    {
    expressionResult.And(res => res.Field<string>("QuartersUniqueCode") == selTopQuarter);
    }
    if (orderAscOrDesc == "DESC")
    {
    dataList = cacheList.AsQueryable().Where(expressionResult).OrderByDescending(row => row.Field<int>("StaffId")).Select(row => row).Skip(skipNum).Take(pageSize);
    }
    else
    {
    dataList = cacheList.AsQueryable().Where(expressionResult).OrderBy(row => row.Field<int>("StaffId")).Select(row => row).Skip(skipNum).Take(pageSize);
    }
    DataTable tempDt = new DataTable();
    foreach (DataRow dtrow in dataList)
    {
    object[] o = dtrow.ItemArray;
    DataRow dr= tempDt.NewRow();
    dr = dtrow;
    tempDt.Rows.Add(dr);
    }
    return new QueryResult();
    }
    catch (Exception ex)
    {
    throw ex;
    }


    }

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  • 原文地址:https://www.cnblogs.com/msql/p/3277000.html
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