public static Expression <Func <T, bool> > Or <T>(this Expression <Func <T, bool> > exp_left, Expression <Func <T, bool> > exp_right)
{
var candidateExpr = Expression.Parameter(typeof(T), "candidate");
var parameterReplacer = new ParameterReplacer(candidateExpr);
var left = parameterReplacer.Replace(exp_left.Body);
var right = parameterReplacer.Replace(exp_right.Body);
var body = Expression.Or(left, right);
return(Expression.Lambda <Func <T, bool> >(body, candidateExpr));
}
/// <summary>
/// 表达式参数类型转换
/// </summary>
/// <typeparam name="TNew">新类型</typeparam>
/// <param name="expression">表达式</param>
/// <returns></returns>
public static Expression <Func <TNew, bool> > Cast <TNew>(this LambdaExpression expression)
{
var candidateExpr = Expression.Parameter(typeof(TNew), Where.ParamterName);
var parameterReplacer = new ParameterReplacer(candidateExpr);
var body = parameterReplacer.Replace(expression.Body);
return(Expression.Lambda <Func <TNew, bool> >(body, candidateExpr));
}
/// <summary>
/// 将表达式参数类型转换
/// </summary>
/// <typeparam name="TNew">新类型</typeparam>
/// <param name="expression">表达式</param>
/// <exception cref="ArgumentNullException"></exception>
/// <returns></returns>
public static Expression <Func <TNew, bool> > Cast <TNew>(this LambdaExpression expression)
{
if (expression == null)
{
throw new ArgumentNullException(nameof(expression));
}
var parameter = Expression.Parameter(typeof(TNew), Predicate.ParamterName);
var parameterReplacer = new ParameterReplacer(parameter);
var body = parameterReplacer.Replace(expression.Body);
return(Expression.Lambda <Func <TNew, bool> >(body, parameter));
}