在自己做框架时候遇到一个对条件拼装问题。用lambda写法却无法转换成对象加以组合。直到找到下面这些代码
那么可以直接将lambda表达式解析成SQL条件语句
WhereClip<Admin_User> where = new WhereClip<Admin_User>(a => a.User_NikeName == "ssdf" || a.User_RegIP == "dddd");
where.And(a=>a.User_Email=="dddd");
where.And(a => a.User_Name == "dddd");
where.Or(a => a.User_Status > 2);如下
(([User_NikeName] = @User_NikeName) OR ([User_RegIP] = @User_RegIP))AND([User_Email] = @User_Email)AND([User_Name] = @User_Name)AND([User_Status] > @User_Status)
当然我自己加上了参数化了，具体如何写可以适当加以改写
主要代码：
internal class ConditionBuilder : ExpressionVisitor
{
private Hashtable m_arguments;
private Stack<string> m_conditionParts;
public string Condition { get; private set; }
public Hashtable Arguments { get; private set; }
public void Build(Expression expression)
{
PartialEvaluator evaluator = new PartialEvaluator();
Expression evaluatedExpression = evaluator.Eval(expression);
this.m_arguments = new Hashtable();
this.m_conditionParts = new Stack<string>();
this.Visit(evaluatedExpression);
this.Arguments = m_arguments;
this.Condition = this.m_conditionParts.Count > 0 ? this.m_conditionParts.Pop() : null;
}
protected override Expression VisitBinary(BinaryExpression b)
{
if (b == null) return b;
string opr;
switch (b.NodeType)
{
case ExpressionType.Equal:
opr = "=";
break;
case ExpressionType.NotEqual:
opr = "<>";
break;
case ExpressionType.GreaterThan:
opr = ">";
break;
case ExpressionType.GreaterThanOrEqual:
opr = ">=";
break;
case ExpressionType.LessThan:
opr = "<";
break;
case ExpressionType.LessThanOrEqual:
opr = "<=";
break;
case ExpressionType.AndAlso:
opr = "AND";
break;
case ExpressionType.OrElse:
opr = "OR";
break;
case ExpressionType.Add:
opr = "+";
break;
case ExpressionType.Subtract:
opr = "-";
break;
case ExpressionType.Multiply:
opr = "*";
break;
case ExpressionType.Divide:
opr = "/";
break;
default:
throw new NotSupportedException(b.NodeType + "is not supported.");
}
this.Visit(b.Left);
this.Visit(b.Right);
string right = this.m_conditionParts.Pop();
string left = this.m_conditionParts.Pop();
string condition = String.Format("({0} {1} {2})", left, opr, right);
this.m_conditionParts.Push(condition);
return b;
}
/// <summary>
/// 改写 - 加入数据库参数特殊符号 {@}
/// </summary>
/// <param name="c"></param>
/// <returns></returns>
protected override Expression VisitConstant(ConstantExpression c)
{
if (c == null) return c;
this.m_arguments.Add(m_conditionParts.ToList()[0].Trim('[', ']'), c.Value);
this.m_conditionParts.Push(String.Format("{0}", DbFactoryProviderUser.Provider.GetDbParmChar()) + m_conditionParts.ToList()[0].Trim('[',']'));
return c;
}
/// <summary>
/// 改写-获取属性特性
/// </summary>
/// <param name="m"></param>
/// <returns></returns>
protected override Expression VisitMemberAccess(MemberExpression m)
{
if (m == null) return m;
PropertyInfo propertyInfo = m.Member as PropertyInfo;
if (propertyInfo == null) return m;
this.m_conditionParts.Push(String.Format("[{0}]", propertyInfo.Name));
return m;
}
} public abstract class ExpressionVisitor
{
protected ExpressionVisitor() { }
protected virtual Expression Visit(Expression exp)
{
if (exp == null)
return exp;
switch (exp.NodeType)
{
case ExpressionType.Negate:
case ExpressionType.NegateChecked:
case ExpressionType.Not:
case ExpressionType.Convert:
case ExpressionType.ConvertChecked:
case ExpressionType.ArrayLength:
case ExpressionType.Quote:
case ExpressionType.TypeAs:
return this.VisitUnary((UnaryExpression)exp);
case ExpressionType.Add:
case ExpressionType.AddChecked:
case ExpressionType.Subtract:
case ExpressionType.SubtractChecked:
case ExpressionType.Multiply:
case ExpressionType.MultiplyChecked:
case ExpressionType.Divide:
case ExpressionType.Modulo:
case ExpressionType.And:
case ExpressionType.AndAlso:
case ExpressionType.Or:
case ExpressionType.OrElse:
case ExpressionType.LessThan:
case ExpressionType.LessThanOrEqual:
case ExpressionType.GreaterThan:
case ExpressionType.GreaterThanOrEqual:
case ExpressionType.Equal:
case ExpressionType.NotEqual:
case ExpressionType.Coalesce:
case ExpressionType.ArrayIndex:
case ExpressionType.RightShift:
case ExpressionType.LeftShift:
case ExpressionType.ExclusiveOr:
return this.VisitBinary((BinaryExpression)exp);
case ExpressionType.TypeIs:
return this.VisitTypeIs((TypeBinaryExpression)exp);
case ExpressionType.Conditional:
return this.VisitConditional((ConditionalExpression)exp);
case ExpressionType.Constant:
return this.VisitConstant((ConstantExpression)exp);
case ExpressionType.Parameter:
return this.VisitParameter((ParameterExpression)exp);
case ExpressionType.MemberAccess:
return this.VisitMemberAccess((MemberExpression)exp);
case ExpressionType.Call:
return this.VisitMethodCall((MethodCallExpression)exp);
case ExpressionType.Lambda:
return this.VisitLambda((LambdaExpression)exp);
case ExpressionType.New:
return this.VisitNew((NewExpression)exp);
case ExpressionType.NewArrayInit:
case ExpressionType.NewArrayBounds:
return this.VisitNewArray((NewArrayExpression)exp);
case ExpressionType.Invoke:
return this.VisitInvocation((InvocationExpression)exp);
case ExpressionType.MemberInit:
return this.VisitMemberInit((MemberInitExpression)exp);
case ExpressionType.ListInit:
return this.VisitListInit((ListInitExpression)exp);
default:
throw new Exception(string.Format("Unhandled expression type: '{0}'", exp.NodeType));
}
}
protected virtual MemberBinding VisitBinding(MemberBinding binding)
{
switch (binding.BindingType)
{
case MemberBindingType.Assignment:
return this.VisitMemberAssignment((MemberAssignment)binding);
case MemberBindingType.MemberBinding:
return this.VisitMemberMemberBinding((MemberMemberBinding)binding);
case MemberBindingType.ListBinding:
return this.VisitMemberListBinding((MemberListBinding)binding);
default:
throw new Exception(string.Format("Unhandled binding type '{0}'", binding.BindingType));
}
}
protected virtual ElementInit VisitElementInitializer(ElementInit initializer)
{
ReadOnlyCollection<Expression> arguments = this.VisitExpressionList(initializer.Arguments);
if (arguments != initializer.Arguments)
{
return Expression.ElementInit(initializer.AddMethod, arguments);
}
return initializer;
}
protected virtual Expression VisitUnary(UnaryExpression u)
{
Expression operand = this.Visit(u.Operand);
if (operand != u.Operand)
{
return Expression.MakeUnary(u.NodeType, operand, u.Type, u.Method);
}
return u;
}
protected virtual Expression VisitBinary(BinaryExpression b)
{
Expression left = this.Visit(b.Left);
Expression right = this.Visit(b.Right);
Expression conversion = this.Visit(b.Conversion);
if (left != b.Left || right != b.Right || conversion != b.Conversion)
{
if (b.NodeType == ExpressionType.Coalesce && b.Conversion != null)
return Expression.Coalesce(left, right, conversion as LambdaExpression);
else
return Expression.MakeBinary(b.NodeType, left, right, b.IsLiftedToNull, b.Method);
}
return b;
}
protected virtual Expression VisitTypeIs(TypeBinaryExpression b)
{
Expression expr = this.Visit(b.Expression);
if (expr != b.Expression)
{
return Expression.TypeIs(expr, b.TypeOperand);
}
return b;
}
protected virtual Expression VisitConstant(ConstantExpression c)
{
return c;
}
protected virtual Expression VisitConditional(ConditionalExpression c)
{
Expression test = this.Visit(c.Test);
Expression ifTrue = this.Visit(c.IfTrue);
Expression ifFalse = this.Visit(c.IfFalse);
if (test != c.Test || ifTrue != c.IfTrue || ifFalse != c.IfFalse)
{
return Expression.Condition(test, ifTrue, ifFalse);
}
return c;
}
protected virtual Expression VisitParameter(ParameterExpression p)
{
return p;
}
protected virtual Expression VisitMemberAccess(MemberExpression m)
{
Expression exp = this.Visit(m.Expression);
if (exp != m.Expression)
{
return Expression.MakeMemberAccess(exp, m.Member);
}
return m;
}
protected virtual Expression VisitMethodCall(MethodCallExpression m)
{
Expression obj = this.Visit(m.Object);
IEnumerable<Expression> args = this.VisitExpressionList(m.Arguments);
if (obj != m.Object || args != m.Arguments)
{
return Expression.Call(obj, m.Method, args);
}
return m;
}
protected virtual ReadOnlyCollection<Expression> VisitExpressionList(ReadOnlyCollection<Expression> original)
{
List<Expression> list = null;
for (int i = 0, n = original.Count; i < n; i++)
{
Expression p = this.Visit(original[i]);
if (list != null)
{
list.Add(p);
}
else if (p != original[i])
{
list = new List<Expression>(n);
for (int j = 0; j < i; j++)
{
list.Add(original[j]);
}
list.Add(p);
}
}
if (list != null)
{
return list.AsReadOnly();
}
return original;
}
protected virtual MemberAssignment VisitMemberAssignment(MemberAssignment assignment)
{
Expression e = this.Visit(assignment.Expression);
if (e != assignment.Expression)
{
return Expression.Bind(assignment.Member, e);
}
return assignment;
}
protected virtual MemberMemberBinding VisitMemberMemberBinding(MemberMemberBinding binding)
{
IEnumerable<MemberBinding> bindings = this.VisitBindingList(binding.Bindings);
if (bindings != binding.Bindings)
{
return Expression.MemberBind(binding.Member, bindings);
}
return binding;
}
protected virtual MemberListBinding VisitMemberListBinding(MemberListBinding binding)
{
IEnumerable<ElementInit> initializers = this.VisitElementInitializerList(binding.Initializers);
if (initializers != binding.Initializers)
{
return Expression.ListBind(binding.Member, initializers);
}
return binding;
}
protected virtual IEnumerable<MemberBinding> VisitBindingList(ReadOnlyCollection<MemberBinding> original)
{
List<MemberBinding> list = null;
for (int i = 0, n = original.Count; i < n; i++)
{
MemberBinding b = this.VisitBinding(original[i]);
if (list != null)
{
list.Add(b);
}
else if (b != original[i])
{
list = new List<MemberBinding>(n);
for (int j = 0; j < i; j++)
{
list.Add(original[j]);
}
list.Add(b);
}
}
if (list != null)
return list;
return original;
}
protected virtual IEnumerable<ElementInit> VisitElementInitializerList(ReadOnlyCollection<ElementInit> original)
{
List<ElementInit> list = null;
for (int i = 0, n = original.Count; i < n; i++)
{
ElementInit init = this.VisitElementInitializer(original[i]);
if (list != null)
{
list.Add(init);
}
else if (init != original[i])
{
list = new List<ElementInit>(n);
for (int j = 0; j < i; j++)
{
list.Add(original[j]);
}
list.Add(init);
}
}
if (list != null)
return list;
return original;
}
protected virtual Expression VisitLambda(LambdaExpression lambda)
{
Expression body = this.Visit(lambda.Body);
if (body != lambda.Body)
{
return Expression.Lambda(lambda.Type, body, lambda.Parameters);
}
return lambda;
}
protected virtual NewExpression VisitNew(NewExpression nex)
{
IEnumerable<Expression> args = this.VisitExpressionList(nex.Arguments);
if (args != nex.Arguments)
{
if (nex.Members != null)
return Expression.New(nex.Constructor, args, nex.Members);
else
return Expression.New(nex.Constructor, args);
}
return nex;
}
protected virtual Expression VisitMemberInit(MemberInitExpression init)
{
NewExpression n = this.VisitNew(init.NewExpression);
IEnumerable<MemberBinding> bindings = this.VisitBindingList(init.Bindings);
if (n != init.NewExpression || bindings != init.Bindings)
{
return Expression.MemberInit(n, bindings);
}
return init;
}
protected virtual Expression VisitListInit(ListInitExpression init)
{
NewExpression n = this.VisitNew(init.NewExpression);
IEnumerable<ElementInit> initializers = this.VisitElementInitializerList(init.Initializers);
if (n != init.NewExpression || initializers != init.Initializers)
{
return Expression.ListInit(n, initializers);
}
return init;
}
protected virtual Expression VisitNewArray(NewArrayExpression na)
{
IEnumerable<Expression> exprs = this.VisitExpressionList(na.Expressions);
if (exprs != na.Expressions)
{
if (na.NodeType == ExpressionType.NewArrayInit)
{
return Expression.NewArrayInit(na.Type.GetElementType(), exprs);
}
else
{
return Expression.NewArrayBounds(na.Type.GetElementType(), exprs);
}
}
return na;
}
protected virtual Expression VisitInvocation(InvocationExpression iv)
{
IEnumerable<Expression> args = this.VisitExpressionList(iv.Arguments);
Expression expr = this.Visit(iv.Expression);
if (args != iv.Arguments || expr != iv.Expression)
{
return Expression.Invoke(expr, args);
}
return iv;
}
}public class PartialEvaluator : ExpressionVisitor
{
private Func<Expression, bool> m_fnCanBeEvaluated;
private HashSet<Expression> m_candidates;
public PartialEvaluator()
: this(CanBeEvaluatedLocally)
{ }
public PartialEvaluator(Func<Expression, bool> fnCanBeEvaluated)
{
this.m_fnCanBeEvaluated = fnCanBeEvaluated;
}
public Expression Eval(Expression exp)
{
this.m_candidates = new Nominator(this.m_fnCanBeEvaluated).Nominate(exp);
return this.Visit(exp);
}
protected override Expression Visit(Expression exp)
{
if (exp == null)
{
return null;
}
if (this.m_candidates.Contains(exp))
{
return this.Evaluate(exp);
}
return base.Visit(exp);
}
private Expression Evaluate(Expression e)
{
if (e.NodeType == ExpressionType.Constant)
{
return e;
}
LambdaExpression lambda = Expression.Lambda(e);
Delegate fn = lambda.Compile();
return Expression.Constant(fn.DynamicInvoke(null), e.Type);
}
private static bool CanBeEvaluatedLocally(Expression exp)
{
return exp.NodeType != ExpressionType.Parameter;
}
#region Nominator
/// <summary>
/// Performs bottom-up analysis to determine which nodes can possibly
/// be part of an evaluated sub-tree.
/// </summary>
private class Nominator : ExpressionVisitor
{
private Func<Expression, bool> m_fnCanBeEvaluated;
private HashSet<Expression> m_candidates;
private bool m_cannotBeEvaluated;
internal Nominator(Func<Expression, bool> fnCanBeEvaluated)
{
this.m_fnCanBeEvaluated = fnCanBeEvaluated;
}
internal HashSet<Expression> Nominate(Expression expression)
{
this.m_candidates = new HashSet<Expression>();
this.Visit(expression);
return this.m_candidates;
}
protected override Expression Visit(Expression expression)
{
if (expression != null)
{
bool saveCannotBeEvaluated = this.m_cannotBeEvaluated;
this.m_cannotBeEvaluated = false;
base.Visit(expression);
if (!this.m_cannotBeEvaluated)
{
if (this.m_fnCanBeEvaluated(expression))
{
this.m_candidates.Add(expression);
}
else
{
this.m_cannotBeEvaluated = true;
}
}
this.m_cannotBeEvaluated |= saveCannotBeEvaluated;
}
return expression;
}
}
#endregion
} public class WhereClip<T> : ExpressionClip where T : BaseEntity
{
public WhereClip()
{
if (table == null)
table = new Hashtable();
}
private String whereString;
public override String WhereString
{
get { return whereString; }
set { whereString = value; }
}
public WhereClip(Expression<Func<T, bool>> exp)
{
if (table == null)
table = new Hashtable();
this.And(exp);
}
private Hashtable table;
public override Hashtable Table
{
get { return table; }
set
{
table = value;
}
}
/// <summary>
/// AND 条件
/// </summary>
/// <param name="right"></param>
public void And(Expression<Func<T, bool>> right)
{
ConditionBuilder conditionBuilder = new ConditionBuilder();
conditionBuilder.Build(right.Body);
if (!String.IsNullOrEmpty(conditionBuilder.Condition))
{
whereString += "AND" + conditionBuilder.Condition;
}
foreach (DictionaryEntry item in conditionBuilder.Arguments)
{
if (!table.ContainsKey(item.Key))
table.Add(item.Key, item.Value);
else
table[item.Key] = item.Value;
}
//替换开始字符
if (whereString.StartsWith("AND"))
{
whereString = WhereString.TrimStart('A', 'N', 'D');
}
}
/// <summary>
/// OR 条件
/// </summary>
/// <param name="right"></param>
public void Or(Expression<Func<T, bool>> right)
{
ConditionBuilder conditionBuilder = new ConditionBuilder();
conditionBuilder.Build(right.Body);
if (!String.IsNullOrEmpty(conditionBuilder.Condition))
{
whereString += "OR" + conditionBuilder.Condition;
}
foreach (DictionaryEntry item in conditionBuilder.Arguments)
{
if (!table.ContainsKey(item.Key))
table.Add(item.Key, item.Value);
else
table[item.Key] = item.Value;
}
if (whereString.StartsWith("OR"))
{
whereString = WhereString.TrimStart('O', 'R');
}
}
public WhereClip<T> Not()
{
throw new Exception("未实现");
}public abstract class ExpressionClip : IExpressionClip
{
protected Expression _Expression;
public abstract String WhereString
{
get;
set;
}
public abstract Hashtable Table
{
get;
set;
}
}
代码下载地址：
CSDN：http://download.csdn.net/detail/ysq5202121/4251354
老赵：http://www.cnblogs.com/jeffreyzhao/archive/2008/03/05/linq-to-sql-batch-delete-extension.html