public static Expression <Func <T, bool> > Combine <T>(Expression <Func <T, bool> > expr1, Expression <Func <T, bool> > expr2, OperationEnum op)
{
var parameter = Expression.Parameter(typeof(T));
var leftVisitor = new ReplaceExpressionVisitor(expr1.Parameters[0], parameter);
var left = leftVisitor.Visit(expr1.Body);
var rightVisitor = new ReplaceExpressionVisitor(expr2.Parameters[0], parameter);
var right = rightVisitor.Visit(expr2.Body);
if (op == OperationEnum.AND)
{
return(Expression.Lambda <Func <T, bool> >(Expression.AndAlso(left, right), parameter));
}
else if (op == OperationEnum.OR)
{
return(Expression.Lambda <Func <T, bool> >(Expression.OrElse(left, right), parameter));
}
else
{
throw new NotImplementedException();
}
}
public static Expression <Func <T, bool> > AndAlso <T>(this Expression <Func <T, bool> > expr1, Expression <Func <T, bool> > expr2)
{
if (expr1 == null)
{
throw new ArgumentNullException(nameof(expr1));
}
if (expr2 == null)
{
throw new ArgumentNullException(nameof(expr2));
}
var parameter = Expression.Parameter(typeof(T));
var leftVisitor = new ReplaceExpressionVisitor(expr1.Parameters[0], parameter);
var left = leftVisitor.Visit(expr1.Body);
var rightVisitor = new ReplaceExpressionVisitor(expr2.Parameters[0], parameter);
var right = rightVisitor.Visit(expr2.Body);
Debug.Assert(left != null, "left is null");
Debug.Assert(right != null, "right is null");
return(Expression.Lambda <Func <T, bool> >(Expression.AndAlso(left, right), parameter));
}
/// <summary>
/// 按关键词进行过滤
/// </summary>
protected virtual IQueryable <TEntity> ApplyKeywordFilter(IQueryable <TEntity> query)
{
// 无关键字或无过滤条件时跳过
if (string.IsNullOrEmpty(_request.Keyword) || _keywordConditions.Count == 0)
{
return(query);
}
// 使用or合并所有表达式
var firstCondition = _keywordConditions.First();
var leftParamExpr = firstCondition.Parameters[0];
var leftBodyExpr = firstCondition.Body;
foreach (var condition in _keywordConditions.Skip(1))
{
var rightParamExpr = condition.Parameters[0];
var visitor = new ReplaceExpressionVisitor(rightParamExpr, leftParamExpr);
var rightBodyExpr = visitor.Visit(condition.Body);
leftBodyExpr = Expression.OrElse(leftBodyExpr, rightBodyExpr);
}
var predicate = Expression.Lambda <Func <TEntity, bool> >(leftBodyExpr, leftParamExpr);
return(query.Where(predicate));
}
public static Expression <Func <T, bool> > AndOrCustom <T>(
this Expression <Func <T, bool> > expr1,
Expression <Func <T, bool> > expr2, bool isAnd = true)
{
var parameter = Expression.Parameter(typeof(T));
var leftVisitor = new ReplaceExpressionVisitor(expr1.Parameters[0], parameter);
var left = leftVisitor.Visit(expr1.Body);
var rightVisitor = new ReplaceExpressionVisitor(expr2.Parameters[0], parameter);
var right = rightVisitor.Visit(expr2.Body);
if (isAnd)
{
return(Expression.Lambda <Func <T, bool> >(
Expression.AndAlso(left, right), parameter));
}
else
{
return(Expression.Lambda <Func <T, bool> >(
Expression.Or(left, right), parameter));
}
}
public static Expression <Func <T, bool> > ToExpression <T>(this IEnumerable <FilterRequest> filters)
{
if (filters == null || !filters.Any())
{
return(null);
}
var properties = typeof(T).GetProperties(ReflectionConstants.SearchPropertyFlags);
var param = Expression.Parameter(typeof(T), "p");
List <Expression <Func <T, bool> > > expressions = new List <Expression <Func <T, bool> > >();
foreach (var filter in filters)
{
var prop = properties.FirstOrDefault(x => x.Name == filter.Field);
var propType = prop.PropertyType;
Expression <Func <T, bool> > expression = null;
if (filter.ValueDateTimeFrom != null || filter.ValueDateTimeTo != null)
{
Expression <Func <T, bool> > expressionFrom = null;
Expression <Func <T, bool> > expressionTo = null;
if (filter.ValueDateTimeFrom != null)
{
expressionFrom =
ExpressionHelper.CreateGTEExpression <T>(param, prop.Name, filter.ValueDateTimeFrom.Value);
}
if (filter.ValueDateTimeTo != null)
{
expressionTo =
ExpressionHelper.CreateLTEExpression <T>(param, prop.Name, filter.ValueDateTimeTo.Value);
}
if (expressionFrom != null && expressionTo != null)
{
var leftVisitor = new ReplaceExpressionVisitor(expressionFrom.Parameters[0], param);
var left = leftVisitor.Visit(expressionFrom.Body);
var rightVisitor = new ReplaceExpressionVisitor(expressionTo.Parameters[0], param);
var right = rightVisitor.Visit(expressionTo.Body);
expression = ExpressionHelper.CreateAndExpression <T>(param, left, right);
}
else
{
expression = expressionFrom ?? expressionTo;
}
}
else if (filter.ValueNumberFrom != null || filter.ValueNumberTo != null)
{
Expression <Func <T, bool> > expressionFrom = null;
Expression <Func <T, bool> > expressionTo = null;
if (filter.ValueNumberFrom != null)
{
expressionFrom =
ExpressionHelper.CreateGTEExpression <T>(param, prop.Name, filter.ValueNumberFrom.Value);
}
if (filter.ValueNumberTo != null)
{
expressionTo =
ExpressionHelper.CreateLTEExpression <T>(param, prop.Name, filter.ValueNumberTo.Value);
}
if (expressionFrom != null && expressionTo != null)
{
var leftVisitor = new ReplaceExpressionVisitor(expressionFrom.Parameters[0], param);
var left = leftVisitor.Visit(expressionFrom.Body);
var rightVisitor = new ReplaceExpressionVisitor(expressionTo.Parameters[0], param);
var right = rightVisitor.Visit(expressionTo.Body);
expression = ExpressionHelper.CreateAndExpression <T>(param, left, right);
}
else
{
expression = expressionFrom ?? expressionTo;
}
}
else if (filter.ValueBool != null)
{
expression = ExpressionHelper.CreateEqualExpression <T>(param, prop.Name, filter.ValueBool.Value);
}
else if (filter.ValueList != null)
{
expression = ExpressionHelper.CreateContainExpression <T>(param, prop.Name, filter.ValueList);
}
else
{
expression = ExpressionHelper.CreateContainExpression <T>(param, prop.Name, filter.ValueString, StringComparison.InvariantCultureIgnoreCase);
}
expressions.Add(expression);
}
var result = expressions.FirstOrDefault();
for (int i = 1; i < expressions.Count; i++)
{
var exp = expressions[i];
var leftVisitor = new ReplaceExpressionVisitor(result.Parameters[0], param);
var left = leftVisitor.Visit(result.Body);
var rightVisitor = new ReplaceExpressionVisitor(exp.Parameters[0], param);
var right = rightVisitor.Visit(exp.Body);
result = ExpressionHelper.CreateAndExpression <T>(param, left, right);
}
return(result);
}
