80 lines
2.9 KiB
C#
80 lines
2.9 KiB
C#
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using System;
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using System.Linq.Expressions;
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namespace JSMachine.WMS.Infrastructure.LambdaHelp
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{
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public static class ExpressionExtension
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{
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public static Expression<Func<T, bool>> And<T>(this Expression<Func<T, bool>> expr1, Expression<Func<T, bool>> expr2)
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{
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if (expr1 == null)
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return expr2;
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else if (expr2 == null)
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return expr1;
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//return Expression.Lambda<Func<T, bool>>(Expression.AndAlso(expr1.Body, expr2.Body), expr1.Parameters);
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ParameterExpression newParameter = Expression.Parameter(typeof(T), "c");
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NewExpressionVisitor visitor = new NewExpressionVisitor(newParameter);
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var left = visitor.Replace(expr1.Body);
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var right = visitor.Replace(expr2.Body);
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var body = Expression.And(left, right);
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return Expression.Lambda<Func<T, bool>>(body, newParameter);
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}
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public static Expression<Func<T, bool>> Or<T>(this Expression<Func<T, bool>> expr1, Expression<Func<T, bool>> expr2)
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{
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if (expr1 == null)
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return expr2;
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else if (expr2 == null)
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return expr1;
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ParameterExpression newParameter = Expression.Parameter(typeof(T), "c");
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NewExpressionVisitor visitor = new NewExpressionVisitor(newParameter);
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var left = visitor.Replace(expr1.Body);
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var right = visitor.Replace(expr2.Body);
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var body = Expression.Or(left, right);
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return Expression.Lambda<Func<T, bool>>(body, newParameter);
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}
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//与拼接
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public static Expression<Func<T, bool>> AndAlso<T>(this Expression<Func<T, bool>> a, Expression<Func<T, bool>> b)
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{
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var p = Expression.Parameter(typeof(T), "p");
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var bd = Expression.AndAlso(
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Expression.Invoke(a, p),
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Expression.Invoke(b, p));
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var ld = Expression.Lambda<Func<T, bool>>(bd, p);
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return ld;
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}
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//或拼接
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public static Expression<Func<T, bool>> Orelse<T>(this Expression<Func<T, bool>> a, Expression<Func<T, bool>> b)
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{
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var p = Expression.Parameter(typeof(T), "p");
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var bd = Expression.OrElse(
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Expression.Invoke(a, p),
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Expression.Invoke(b, p));
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var ld = Expression.Lambda<Func<T, bool>>(bd, p);
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return ld;
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}
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}
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internal class NewExpressionVisitor : ExpressionVisitor
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{
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public ParameterExpression _NewParameter { get; private set; }
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public NewExpressionVisitor(ParameterExpression param)
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{
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this._NewParameter = param;
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}
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public Expression Replace(Expression exp)
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{
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return this.Visit(exp);
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}
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protected override Expression VisitParameter(ParameterExpression node)
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{
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return this._NewParameter;
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}
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}
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}
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