internal static (object?value, string?error) TryEvaluateExpression(this IQueryElement expr, EvaluationContext context)
{
if (!context.TryGetValue(expr, out var info))
{
if (TryEvaluateExpressionInternal(expr, context, out var result, out var errorMessage))
{
context.Register(expr, result);
}
else
{
context.RegisterError(expr, errorMessage);
}
return(result, errorMessage);
}
public static bool CanBeEvaluated(this IQueryElement expr, EvaluationContext context)
{
return(expr.TryEvaluateExpression(context, out _, out _));
}
public static bool TryEvaluateExpression(this IQueryElement expr, EvaluationContext context, out object?result)
{
(result, var error) = expr.TryEvaluateExpression(context);
return(error == null);
}
static bool TryEvaluateExpressionInternal(this IQueryElement expr, EvaluationContext context, out object?result, out string?errorMessage)
{
result = null;
errorMessage = null;
switch (expr.ElementType)
{
case QueryElementType.SqlValue: result = ((SqlValue)expr).Value; return(true);
case QueryElementType.SqlParameter:
{
var sqlParameter = (SqlParameter)expr;
if (context.ParameterValues == null)
{
return(false);
}
result = sqlParameter.GetParameterValue(context.ParameterValues).Value;
return(true);
}
case QueryElementType.IsNullPredicate:
{
var isNullPredicate = (SqlPredicate.IsNull)expr;
if (!isNullPredicate.Expr1.TryEvaluateExpression(context, out var value))
{
return(false);
}
result = isNullPredicate.IsNot == (value != null);
return(true);
}
case QueryElementType.ExprExprPredicate:
{
var exprExpr = (SqlPredicate.ExprExpr)expr;
var reduced = exprExpr.Reduce(context);
if (!ReferenceEquals(reduced, expr))
{
return(TryEvaluateExpression(reduced, context, out result, out errorMessage));
}
if (!exprExpr.Expr1.TryEvaluateExpression(context, out var value1) ||
!exprExpr.Expr2.TryEvaluateExpression(context, out var value2))
{
return(false);
}
switch (exprExpr.Operator)
{
case SqlPredicate.Operator.Equal:
{
if (value1 == null)
{
result = value2 == null;
}
else
{
result = (value2 != null) && value1.Equals(value2);
}
break;
}
case SqlPredicate.Operator.NotEqual:
{
if (value1 == null)
{
result = value2 != null;
}
else
{
result = value2 == null || !value1.Equals(value2);
}
break;
}
default:
{
if (!(value1 is IComparable comp1) || !(value2 is IComparable comp2))
{
result = false;
return(true);
}
switch (exprExpr.Operator)
{
case SqlPredicate.Operator.Greater:
result = comp1.CompareTo(comp2) > 0;
break;
case SqlPredicate.Operator.GreaterOrEqual:
result = comp1.CompareTo(comp2) >= 0;
break;
case SqlPredicate.Operator.NotGreater:
result = !(comp1.CompareTo(comp2) > 0);
break;
case SqlPredicate.Operator.Less:
result = comp1.CompareTo(comp2) < 0;
break;
case SqlPredicate.Operator.LessOrEqual:
result = comp1.CompareTo(comp2) <= 0;
break;
case SqlPredicate.Operator.NotLess:
result = !(comp1.CompareTo(comp2) < 0);
break;
default:
return(false);
}
break;
}
}
return(true);
}
case QueryElementType.IsTruePredicate:
{
var isTruePredicate = (SqlPredicate.IsTrue)expr;
if (!isTruePredicate.Expr1.TryEvaluateExpression(context, out var value))
{
return(false);
}
if (value == null)
{
result = false;
return(true);
}
if (value is bool boolValue)
{
result = boolValue != isTruePredicate.IsNot;
return(true);
}
return(false);
}
case QueryElementType.SqlBinaryExpression:
{
var binary = (SqlBinaryExpression)expr;
if (!binary.Expr1.TryEvaluateExpression(context, out var leftEvaluated, out errorMessage))
{
return(false);
}
if (!binary.Expr2.TryEvaluateExpression(context, out var rightEvaluated, out errorMessage))
{
return(false);
}
dynamic?left = leftEvaluated;
dynamic?right = rightEvaluated;
if (left == null || right == null)
{
return(true);
}
switch (binary.Operation)
{
case "+": result = left + right; break;
case "-": result = left - right; break;
case "*": result = left * right; break;
case "/": result = left / right; break;
case "%": result = left % right; break;
case "^": result = left ^ right; break;
case "&": result = left & right; break;
case "<": result = left < right; break;
case ">": result = left > right; break;
case "<=": result = left <= right; break;
case ">=": result = left >= right; break;
default:
errorMessage = $"Unknown binary operation '{binary.Operation}'.";
return(false);
}
return(true);
}
case QueryElementType.SqlFunction:
{
var function = (SqlFunction)expr;
switch (function.Name)
{
case "CASE":
{
if (function.Parameters.Length != 3)
{
errorMessage = "CASE function expected to have 3 parameters.";
return(false);
}
if (!function.Parameters[0]
.TryEvaluateExpression(context, out var cond, out errorMessage))
{
return(false);
}
if (!(cond is bool))
{
errorMessage =
$"CASE function expected to have boolean condition (was: {cond?.GetType()}).";
return(false);
}
if ((bool)cond !)
{
return(function.Parameters[1]
.TryEvaluateExpression(context, out result, out errorMessage));
}
else
{
return(function.Parameters[2]
.TryEvaluateExpression(context, out result, out errorMessage));
}
}
case "Length":
{
if (function.Parameters[0]
.TryEvaluateExpression(context, out var strValue, out errorMessage))
{
if (strValue == null)
{
return(true);
}
if (strValue is string str)
{
result = str.Length;
return(true);
}
}
return(false);
}
case "$ToLower$":
{
if (function.Parameters[0]
.TryEvaluateExpression(context, out var strValue, out errorMessage))
{
if (strValue == null)
{
return(true);
}
if (strValue is string str)
{
result = str.ToLower(CultureInfo.InvariantCulture);
return(true);
}
}
return(false);
}
case "$ToUpper$":
{
if (function.Parameters[0]
.TryEvaluateExpression(context, out var strValue, out errorMessage))
{
if (strValue == null)
{
return(true);
}
if (strValue is string str)
{
result = str.ToUpper(CultureInfo.InvariantCulture);
return(true);
}
}
return(false);
}
default:
errorMessage = $"Unknown function '{function.Name}'.";
return(false);
}
}
default:
{
return(false);
}
}
}
public static EvaluationContext.EvaluationInfo TryEvaluateExpression(this IQueryElement expr, EvaluationContext context)
{
if (!context.TryGetValue(expr, out var info))
{
var canBeEvaluated =
TryEvaluateExpressionInternal(expr, context, out var result, out var errorMessage);
info = new EvaluationContext.EvaluationInfo(canBeEvaluated, result, errorMessage);
context.Register(expr, info);
return(info);
}
return(info !);
}
public ISqlPredicate Reduce(EvaluationContext context)
{
if (Operator == Operator.Equal || Operator == Operator.NotEqual)
{
if (Expr1.TryEvaluateExpression(context, out var value1))
{
if (value1 == null)
{
return(new IsNull(Expr2, Operator != Operator.Equal));
}
}
else if (Expr2.TryEvaluateExpression(context, out var value2))
{
if (value2 == null)
{
return(new IsNull(Expr1, Operator != Operator.Equal));
}
}
}
if (WithNull == null)
{
return(this);
}
var canBeNull_1 = Expr1.ShouldCheckForNull();
var canBeNull_2 = Expr2.ShouldCheckForNull();
var isInverted = !WithNull.Value;
var predicate = new ExprExpr(Expr1, Operator, Expr2, null);
if (!canBeNull_1 && !canBeNull_2)
{
return(predicate);
}
var search = new SqlSearchCondition();
if (Expr1.CanBeEvaluated(context))
{
if (!Expr2.CanBeEvaluated(context))
{
if (canBeNull_2)
{
if (isInverted)
{
if (Operator != Operator.Equal)
{
search.Conditions.Add(new SqlCondition(false, predicate, true));
search.Conditions.Add(new SqlCondition(false, new IsNull(Expr2, false), false));
}
}
else if (Operator == Operator.NotEqual)
{
search.Conditions.Add(new SqlCondition(false, predicate, true));
search.Conditions.Add(new SqlCondition(false, new IsNull(Expr2, false), false));
}
}
}
}
else if (Expr2.CanBeEvaluated(context))
{
if (canBeNull_1)
{
if (isInverted)
{
if (Operator != Operator.Equal)
{
search.Conditions.Add(new SqlCondition(false, predicate, true));
search.Conditions.Add(new SqlCondition(false, new IsNull(Expr1, false), false));
}
}
else if (Operator == Operator.NotEqual)
{
search.Conditions.Add(new SqlCondition(false, predicate, true));
search.Conditions.Add(new SqlCondition(false, new IsNull(Expr1, false), false));
}
}
}
else
{
if (canBeNull_2)
{
if (canBeNull_1)
{
if (isInverted)
{
if (Operator == Operator.Equal)
{
search.Conditions.Add(new SqlCondition(false, predicate, true));
search.Conditions.Add(new SqlCondition(false, new IsNull(Expr1, false), false));
search.Conditions.Add(new SqlCondition(false, new IsNull(Expr2, true), true));
search.Conditions.Add(new SqlCondition(false, new IsNull(Expr1, true), false));
search.Conditions.Add(new SqlCondition(false, new IsNull(Expr2, false), false));
}
else
if (Operator == Operator.NotEqual)
{
search.Conditions.Add(new SqlCondition(false, predicate, true));
search.Conditions.Add(new SqlCondition(false, new IsNull(Expr1, false), false));
search.Conditions.Add(new SqlCondition(false, new IsNull(Expr2, true), true));
search.Conditions.Add(new SqlCondition(false, new IsNull(Expr1, true), false));
search.Conditions.Add(new SqlCondition(false, new IsNull(Expr2, false), false));
}
else
if (Operator == Operator.LessOrEqual || Operator == Operator.GreaterOrEqual)
{
search.Conditions.Add(new SqlCondition(false, predicate, true));
search.Conditions.Add(new SqlCondition(false, new IsNull(Expr1, false), true));
search.Conditions.Add(new SqlCondition(false, new IsNull(Expr2, false), false));
}
else if (Operator == Operator.NotEqual)
{
search.Conditions.Add(new SqlCondition(false, predicate, true));
search.Conditions.Add(new SqlCondition(false, new IsNull(Expr1, false), false));
search.Conditions.Add(new SqlCondition(false, new IsNull(Expr2, false), false));
}
else
{
search.Conditions.Add(new SqlCondition(false, predicate, true));
search.Conditions.Add(new SqlCondition(false, new IsNull(Expr1, false), false));
search.Conditions.Add(new SqlCondition(false, new IsNull(Expr2, false), false));
}
}
else if (Operator == Operator.Equal)
{
search.Conditions.Add(new SqlCondition(false, predicate, true));
search.Conditions.Add(new SqlCondition(false, new IsNull(Expr1, false), false));
search.Conditions.Add(new SqlCondition(false, new IsNull(Expr2, false), false));
}
else if (Operator == Operator.NotEqual)
{
search.Conditions.Add(new SqlCondition(false, predicate, true));
search.Conditions.Add(new SqlCondition(false, new IsNull(Expr1, false), false));
search.Conditions.Add(new SqlCondition(false, new IsNull(Expr2, true), true));
search.Conditions.Add(new SqlCondition(false, new IsNull(Expr1, true), false));
search.Conditions.Add(new SqlCondition(false, new IsNull(Expr2, false), false));
}
}
else
if (isInverted)
{
search.Conditions.Add(new SqlCondition(false, predicate, true));
search.Conditions.Add(new SqlCondition(false, new IsNull(Expr2, false), false));
}
}
else
{
if (canBeNull_1)
{
if (isInverted)
{
search.Conditions.Add(new SqlCondition(false, predicate, true));
search.Conditions.Add(new SqlCondition(false, new IsNull(Expr1, false), false));
}
}
else
{
search.Conditions.Add(new SqlCondition(false, predicate, true));
search.Conditions.Add(new SqlCondition(false, new IsNull(Expr1, false), false));
search.Conditions.Add(new SqlCondition(false, new IsNull(Expr2, false), false));
}
}
}
if (search.Conditions.Count == 0)
{
return(predicate);
}
return(search);
}
