本文代码转自这篇文章，先做下记录。

    public static class LambdaUtil<T>{/// <summary>/// lambda表达式:t=>true/// </summary>/// <returns></returns>public static Expression<Func<T, bool>> True(){return t => true;}/// <summary>/// lambda表达式:t=>false/// </summary>/// <returns></returns>public static Expression<Func<T, bool>> False(){return t => false;}/// <summary>/// lambda表达式:t=>t.propName/// 多用于order排序/// </summary>/// <typeparam name="T">参数类型</typeparam>/// <typeparam name="TKey">返回类型</typeparam>/// <param name="propName">属性名</param>/// <returns></returns>private static Expression<Func<T, TKey>> Order<TKey>(string propName){// 创建节点参数tParameterExpression parameter = Expression.Parameter(typeof(T), "t");// 创建一个属性MemberExpression property = Expression.Property(parameter, propName);// 生成lambda表达式return Expression.Lambda<Func<T, TKey>>(property, parameter);}/// <summary>/// lambda表达式:t=>t.propName==propValue/// 多用于where条件/// </summary>/// <typeparam name="T">参数类型</typeparam>/// <param name="propName">属性名称</param>/// <param name="propValue">属性值</param>/// <returns></returns>public static Expression<Func<T, bool>> Equal(string propName, object propValue){// 创建节点参数tParameterExpression parameter = Expression.Parameter(typeof(T), "t");// 创建一个成员(字段/属性)MemberExpression member = Expression.PropertyOrField(parameter, propName);// 创建一个常数ConstantExpression constant = Expression.Constant(propValue);// 创建一个相等比较ExpressionBinaryExpression binary = Expression.Equal(member, constant);// 生成lambda表达式return Expression.Lambda<Func<T, bool>>(binary, parameter);}/// <summary>/// lambda表达式:t=>t.propName!=propValue/// 多用于where条件/// </summary>/// <typeparam name="T">参数类型</typeparam>/// <param name="propName">属性名称</param>/// <param name="propValue">属性值</param>/// <returns></returns>public static Expression<Func<T, bool>> NotEqual(string propName, object propValue){// 创建节点参数tParameterExpression parameter = Expression.Parameter(typeof(T), "t");// 创建一个成员(字段/属性)MemberExpression member = Expression.PropertyOrField(parameter, propName);// 创建一个常数ConstantExpression constant = Expression.Constant(propValue);// 创建一个不相等比较ExpressionBinaryExpression binary = Expression.NotEqual(member, constant);// 生成lambda表达式return Expression.Lambda<Func<T, bool>>(binary, parameter);}/// <summary>/// lambda表达式:t=>t.propName&lt;propValue/// 多用于where条件/// </summary>/// <typeparam name="T">参数类型</typeparam>/// <param name="propName">属性名称</param>/// <param name="propValue">属性值</param>/// <returns></returns>public static Expression<Func<T, bool>> LessThan(string propName, object propValue){// 创建节点参数tParameterExpression parameter = Expression.Parameter(typeof(T), "t");// 创建一个成员(字段/属性)MemberExpression member = Expression.PropertyOrField(parameter, propName);// 创建一个常数ConstantExpression constant = Expression.Constant(propValue);// 创建一个不相等比较ExpressionBinaryExpression binary = Expression.LessThan(member, constant);// 生成lambda表达式return Expression.Lambda<Func<T, bool>>(binary, parameter);}/// <summary>/// lambda表达式:t=>t.propName&lt;=propValue/// 多用于where条件/// </summary>/// <typeparam name="T">参数类型</typeparam>/// <param name="propName">属性名称</param>/// <param name="propValue">属性值</param>/// <returns></returns>public static Expression<Func<T, bool>> LessThanOrEqual(string propName, object propValue){// 创建节点参数tParameterExpression parameter = Expression.Parameter(typeof(T), "t");// 创建一个成员(字段/属性)MemberExpression member = Expression.PropertyOrField(parameter, propName);// 创建一个常数ConstantExpression constant = Expression.Constant(propValue);// 创建一个不相等比较ExpressionBinaryExpression binary = Expression.LessThanOrEqual(member, constant);// 生成lambda表达式return Expression.Lambda<Func<T, bool>>(binary, parameter);}/// <summary>/// lambda表达式:t=>t.propName>propValue/// 多用于where条件/// </summary>/// <typeparam name="T">参数类型</typeparam>/// <param name="propName">属性名称</param>/// <param name="propValue">属性值</param>/// <returns></returns>public static Expression<Func<T, bool>> GreaterThan(string propName, object propValue){// 创建节点参数tParameterExpression parameter = Expression.Parameter(typeof(T), "t");// 创建一个成员(字段/属性)MemberExpression member = Expression.PropertyOrField(parameter, propName);// 创建一个常数ConstantExpression constant = Expression.Constant(propValue);// 创建一个不相等比较ExpressionBinaryExpression binary = Expression.GreaterThan(member, constant);// 生成lambda表达式return Expression.Lambda<Func<T, bool>>(binary, parameter);}/// <summary>/// lambda表达式:t=>t.propName>=propValue/// 多用于where条件/// </summary>/// <typeparam name="T">参数类型</typeparam>/// <param name="propName">属性名称</param>/// <param name="propValue">属性值</param>/// <returns></returns>public static Expression<Func<T, bool>> GreaterThanOrEqual(string propName, object propValue){// 创建节点参数tParameterExpression parameter = Expression.Parameter(typeof(T), "t");// 创建一个成员(字段/属性)MemberExpression member = Expression.PropertyOrField(parameter, propName);// 创建一个常数ConstantExpression constant = Expression.Constant(propValue);// 创建一个不相等比较ExpressionBinaryExpression binary = Expression.GreaterThanOrEqual(member, constant);// 生成lambda表达式return Expression.Lambda<Func<T, bool>>(binary, parameter);}/// <summary>/// lambda表达式:t=>{t.contains(propvalue1) ||...||t.contains(propvalueN)}/// 多用于where条件/// </summary>/// <typeparam name="T">参数类型</typeparam>/// <param name="propName">属性名称</param>/// <param name="propValues">属性值数组</param>/// <returns></returns>public static Expression<Func<T, bool>> In(string propName, string[] propValues){// 创建节点参数tParameterExpression parameter = Expression.Parameter(typeof(T), "t"); // left// 创建一个成员(字段/属性)MemberExpression member = Expression.PropertyOrField(parameter, propName);// 创建一个常数Expression constant = Expression.Constant(false);// 创建一个方法MethodInfo method = typeof(string).GetMethod("Contains", new[] { typeof(string) });foreach (string item in propValues){// 创建一个带参数方法ExpressionMethodCallExpression methodCall = Expression.Call(member, method, Expression.Constant(item)); // right// 连接参数方法constant = Expression.Or(methodCall, constant);}// 生成lambda表达式return Expression.Lambda<Func<T, bool>>(constant, new ParameterExpression[] { parameter });}/// <summary>/// lambda表达式:t=>{!(t.contains(propvalue1) ||...||t.contains(propvalueN))}/// 多用于where条件/// </summary>/// <typeparam name="T">参数类型</typeparam>/// <param name="propName">属性名称</param>/// <param name="propValues">属性值数组</param>/// <returns></returns>public static Expression<Func<T, bool>> NotIn(string propName, string[] propValues){// 创建节点参数tParameterExpression parameter = Expression.Parameter(typeof(T), "t");// 创建一个成员(字段/属性)MemberExpression member = Expression.PropertyOrField(parameter, propName);// 创建一个常数Expression constant = Expression.Constant(false);// 创建一个方法MethodInfo method = typeof(string).GetMethod("Contains", new[] { typeof(string) });foreach (string item in propValues){// 创建一个带参数方法ExpressionMethodCallExpression methodCall = Expression.Call(member, method, Expression.Constant(item)); // right// 连接参数方法constant = Expression.Or(methodCall, constant);}// 生成lambda表达式return Expression.Lambda<Func<T, bool>>(Expression.Not(constant), new ParameterExpression[] { parameter });}/// <summary>/// lambda表达式:t=>t.propName.Contains(propValue)/// 多用于where条件/// </summary>/// <typeparam name="T">参数类型</typeparam>/// <param name="propName">属性名称</param>/// <param name="propValue">属性值</param>/// <returns></returns>public static Expression<Func<T, bool>> Contains(string propName, string propValue){// 创建节点参数tParameterExpression parameter = Expression.Parameter(typeof(T), "t");// 创建一个成员(字段/属性)MemberExpression member = Expression.PropertyOrField(parameter, propName);// 创建一个常数ConstantExpression constant = Expression.Constant(propValue, typeof(string));// 创建一个方法MethodInfo method = typeof(string).GetMethod("Contains", new[] { typeof(string) });// 创建一个带参数方法ExpressionMethodCallExpression methodCall = Expression.Call(member, method, constant);// 生成lambda表达式return Expression.Lambda<Func<T, bool>>(methodCall, parameter);}/// <summary>/// lambda表达式:t=>t.propName.Contains(propValue)/// 多用于where条件/// </summary>/// <typeparam name="T">参数类型</typeparam>/// <param name="propName">属性名称</param>/// <param name="propValue">属性值</param>/// <returns></returns>public static Expression<Func<T, bool>> StartWith(string propName, string propValue){// 创建节点参数tParameterExpression parameter = Expression.Parameter(typeof(T), "t");// 创建一个成员(字段/属性)MemberExpression member = Expression.PropertyOrField(parameter, propName);// 创建一个常数ConstantExpression constant = Expression.Constant(propValue, typeof(string));// 创建一个方法MethodInfo method = typeof(string).GetMethod("StartsWith", new[] { typeof(string) });// 创建一个带参数方法ExpressionMethodCallExpression methodCall = Expression.Call(member, method, constant);// 生成lambda表达式return Expression.Lambda<Func<T, bool>>(methodCall, parameter);}/// <summary>/// lambda表达式:t=>t.propName.Contains(propValue)/// 多用于where条件/// </summary>/// <typeparam name="T">参数类型</typeparam>/// <param name="propName">属性名称</param>/// <param name="propValue">属性值</param>/// <returns></returns>public static Expression<Func<T, bool>> EndsWith(string propName, string propValue){// 创建节点参数tParameterExpression parameter = Expression.Parameter(typeof(T), "t");// 创建一个成员(字段/属性)MemberExpression member = Expression.PropertyOrField(parameter, propName);// 创建一个常数ConstantExpression constant = Expression.Constant(propValue, typeof(string));// 创建一个方法MethodInfo method = typeof(string).GetMethod("EndsWith", new[] { typeof(string) });// 创建一个带参数方法ExpressionMethodCallExpression methodCall = Expression.Call(member, method, constant);// 生成lambda表达式return Expression.Lambda<Func<T, bool>>(methodCall, parameter);}/// <summary>/// lambda表达式:!(t=>t.propName.Contains(propValue))/// 多用于where条件/// </summary>/// <typeparam name="T">参数类型</typeparam>/// <param name="propName">属性名称</param>/// <param name="propValue">属性值</param>/// <returns></returns>public static Expression<Func<T, bool>> NotContains(string propName, string propValue){// 创建节点参数tParameterExpression parameter = Expression.Parameter(typeof(T), "t");// 创建一个成员(字段/属性)MemberExpression member = Expression.PropertyOrField(parameter, propName);// 创建一个常数ConstantExpression constant = Expression.Constant(propValue, typeof(string));// 创建一个方法MethodInfo method = typeof(string).GetMethod("Contains", new[] { typeof(string) });// 创建一个带参数方法ExpressionMethodCallExpression methodCall = Expression.Call(member, method, constant);// 生成lambda表达式return Expression.Lambda<Func<T, bool>>(Expression.Not(methodCall), parameter);}/// <summary>/// lambda表达式:t=>{left and right}/// 多用于where条件/// </summary>/// <param name="left">左侧条件</param>/// <param name="right">右侧条件</param>/// <returns></returns>public static Expression<Func<T, bool>> And(Expression<Func<T, bool>> left, Expression<Func<T, bool>> right){// 创建参数表达式InvocationExpression invocation = Expression.Invoke(right, left.Parameters.Cast<Expression>());// 创建and运算BinaryExpression binary = Expression.And(left.Body, invocation);// 生成lambda表达式return Expression.Lambda<Func<T, bool>>(binary, left.Parameters);}/// <summary>/// lambda表达式:t=>{left or right}/// 多用于where条件/// </summary>/// <param name="left">左侧条件</param>/// <param name="right">右侧条件</param>/// <returns></returns>public static Expression<Func<T, bool>> Or(Expression<Func<T, bool>> left, Expression<Func<T, bool>> right){// 创建参数表达式InvocationExpression invocation = Expression.Invoke(right, left.Parameters.Cast<Expression>());// 创建or运算BinaryExpression binary = Expression.Or(left.Body, invocation);// 生成lambda表达式return Expression.Lambda<Func<T, bool>>(binary, left.Parameters);}}