protected virtual void VisitConstant(ConstantExpression c, SqlVistorFlag flag)
{
var value = c.Value ?? "null";
if (flag.is_right)
{
var paraName = GetCustomParaName(flag.para_pretoken); // flag.GetCustomParaName();
flag.Append(paraName, true);
if (c.Type.IsEnum)
{
AddParameter(paraName, (int)c.Value);
}
else if (c.Type == typeof(bool))
{
AddParameter(paraName, (bool)value ? 1 : 0);
}
else
{
AddParameter(paraName, value);
}
}
else
{
flag.Append(value.ToString());
}
}
protected virtual void VisitUnary(UnaryExpression u, SqlVistorFlag flag)
{
var nodeType = flag.unary_type;
flag.unary_type = u.NodeType;
Visit(u.Operand, flag);
flag.unary_type = nodeType;
}
private void MethodCallLike(MethodCallExpression exp, SqlVistorFlag flag)
{
Visit(exp.Object, flag);
flag.Append(GetUnaryOperater(flag.unary_type));
flag.Append(" LIKE CONCAT('%',");
VisitRight(exp.Arguments[0], flag);
flag.Append(",'%')");
}
/// <summary>
/// 递归解析时，保留上层的IsRight状态
/// </summary>
/// <param name="exp"></param>
/// <param name="flag"></param>
protected virtual void VisitRight(Expression exp, SqlVistorFlag flag)
{
var isRight = flag.is_right;
flag.is_right = true;
Visit(exp, flag);
flag.is_right = isRight; // 回归
}
protected virtual void VisitNew(NewExpression nex, SqlVistorFlag flag)
{
for (var i = 0; i < nex.Members.Count; i++)
{
var arg = nex.Arguments[i];
var member = nex.Members[i];
flag.Append(flag.GetColName(member.Name)).Append("=");
VisitRight(arg, flag);
}
}
protected virtual void VisitMethodCall(MethodCallExpression exp, SqlVistorFlag flag)
{
var methodName = exp.Method.Name;
switch (methodName) //这里其实还可以改成反射调用，不用写switch
{
case "Contains":
MethodCallLike(exp, flag);
break;
// todo 补充其他方法
}
}
protected virtual void VisitMember(MemberExpression exp, SqlVistorFlag flag)
{
if (exp.Expression != null &&
exp.Expression.NodeType == ExpressionType.Parameter)
{
if (flag.is_right && flag.vistor_type == SqlVistorType.Update)
{
var proParaName = flag.GetParaName(exp.Member.Name);
flag.Append(proParaName, true);
AddMemberProperty(proParaName, exp.Member.Name);
}
else
{
if (exp.Member.DeclaringType.GetTypeInfo().IsGenericType &&
exp.Member.DeclaringType?.GetGenericTypeDefinition() == typeof(Nullable <>))
{
if (exp.Member.Name == "Value")
{
Visit(exp.Expression, flag);
}
if (exp.Member.Name != "HasValue")
{
return;
}
var doesNotEqualNull = Expression.MakeBinary(ExpressionType.NotEqual, exp.Expression,
Expression.Constant(null));
Visit(doesNotEqualNull, flag);
}
else
{
flag.Append(flag.GetColName(exp.Member.Name), true);
}
}
}
else
{
var value = Expression.Lambda(exp).Compile().DynamicInvoke();
Visit(Expression.Constant(value), flag);
}
}
protected void VisitNewArray(NewArrayExpression na, SqlVistorFlag flag)
{
var original = na.Expressions;
for (int i = 0, n = original.Count; i < n; i++)
{
var e = original[i];
if (e.NodeType == ExpressionType.NewArrayInit ||
e.NodeType == ExpressionType.NewArrayBounds)
{
if (e is NewArrayExpression newArrayExpression)
{
VisitNewArray(newArrayExpression, flag);
}
}
else
{
Visit(e, flag);
}
}
}
protected virtual void VisitBinary(BinaryExpression exp, SqlVistorFlag flag)
{
var operand = GetBinaryOperater(exp.NodeType);
if (exp.NodeType == ExpressionType.AndAlso ||
exp.NodeType == ExpressionType.OrElse)
{
flag.Append("(");
Visit(exp.Left, flag);
flag.Append(") ").Append(operand).Append(" (");
Visit(exp.Right, flag);
flag.Append(")");
}
else
{
Visit(exp.Left, flag);
flag.Append(operand);
VisitRight(exp.Right, flag);
}
}
/// <summary>
/// 处理where条件表达式，如果表达式为空，默认使用Id
/// </summary>
/// <param name="visitor"></param>
/// <param name="exp"></param>
/// <param name="visType"></param>
private static string GetVisitExpressSql(SqlExpressionVisitor visitor, Expression exp, SqlVistorType visType)
{
if (visType == SqlVistorType.Update)
{
var updateFlag = new SqlVistorFlag(SqlVistorType.Update);
visitor.Visit(exp, updateFlag);
return(updateFlag.sql);
}
string sql;
if (exp == null)
{
throw new ArgumentNullException("whereExp", "where表达式不能为空！");
}
else
{
var whereFlag = new SqlVistorFlag(SqlVistorType.Where);
visitor.Visit(exp, whereFlag);
sql = string.Concat(" WHERE ", whereFlag.sql);
}
return(sql);
}
/// <summary>
/// 递归解析方法入口
/// </summary>
/// <param name="exp"></param>
/// <param name="flag"></param>
public virtual void Visit(Expression exp, SqlVistorFlag flag)
{
switch (exp.NodeType)
{
case ExpressionType.Lambda:
VisitLambda(exp as LambdaExpression, flag);
break;
case ExpressionType.MemberAccess:
VisitMember(exp as MemberExpression, flag);
break;
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:
VisitBinary(exp as BinaryExpression, flag);
break;
case ExpressionType.Negate:
case ExpressionType.NegateChecked:
case ExpressionType.Not:
case ExpressionType.Convert:
case ExpressionType.ConvertChecked:
case ExpressionType.ArrayLength:
case ExpressionType.Quote:
case ExpressionType.TypeAs:
VisitUnary(exp as UnaryExpression, flag);
break;
case ExpressionType.Constant:
VisitConstant(exp as ConstantExpression, flag);
break;
case ExpressionType.Parameter:
VisitParameter(exp as ParameterExpression, flag);
break;
case ExpressionType.Call:
VisitMethodCall(exp as MethodCallExpression, flag);
break;
case ExpressionType.New:
VisitNew(exp as NewExpression, flag);
break;
case ExpressionType.NewArrayInit:
case ExpressionType.NewArrayBounds:
VisitNewArray(exp as NewArrayExpression, flag);
break;
case ExpressionType.MemberInit:
VisitMemberInit(exp as MemberInitExpression, flag);
break;
case ExpressionType.Conditional:
VisitConditional(exp as ConditionalExpression);
break;
}
}
protected virtual void VisitParameter(ParameterExpression parameterExpression, SqlVistorFlag flag)
{
// todo
}
protected virtual void VisitMemberInit(MemberInitExpression memberInitExpression, SqlVistorFlag flag)
{
// todo
}
protected virtual void VisitLambda(LambdaExpression lambda, SqlVistorFlag flag)
{
Visit(lambda.Body, flag);
}