/// <summary>
/// extracts values from equality expressions that match parameter names
/// </summary>
/// <param name="be">binary expression to evaluate</param>
/// <returns>binary expression - supports recursive tree traversal in visitor</returns>
protected override Expression VisitBinary(BinaryExpression be)
{
if (be.NodeType == ExpressionType.Equal ||
be.NodeType == ExpressionType.GreaterThan ||
be.NodeType == ExpressionType.GreaterThanOrEqual ||
be.NodeType == ExpressionType.LessThan ||
be.NodeType == ExpressionType.LessThanOrEqual ||
be.NodeType == ExpressionType.NotEqual)
{
foreach (var param in ParameterNames)
{
if (ExpressionTreeHelpers.IsMemberEqualsValueExpression(be, typeof(T), param))
{
parameters.Add(param, ExpressionTreeHelpers.GetValueFromEqualsExpression(be, typeof(T), param));
return(be);
}
}
return(base.VisitBinary(be));
}
else
{
return(base.VisitBinary(be));
}
}
/// <summary>
/// test to see if expression is a binary expression that checks equality with a constant value
/// - essentially, the caller wants to know if this is a well-formed expression with certain criteria
/// </summary>
/// <param name="exp">expression to check</param>
/// <param name="declaringType">type containing member</param>
/// <param name="memberName">member being checked</param>
/// <returns>true if member is being checked for equality with value</returns>
internal static bool IsMemberEqualsValueExpression(Expression exp, Type declaringType, string memberName)
{
if (exp.NodeType != ExpressionType.Equal)
{
return(false);
}
BinaryExpression be = (BinaryExpression)exp;
// Assert.
if (ExpressionTreeHelpers.IsSpecificMemberExpression(be.Left, declaringType, memberName) &&
ExpressionTreeHelpers.IsSpecificMemberExpression(be.Right, declaringType, memberName))
{
throw new Exception("Cannot have 'member' == 'member' in an expression!");
}
return(ExpressionTreeHelpers.IsSpecificMemberExpression(be.Left, declaringType, memberName) ||
ExpressionTreeHelpers.IsSpecificMemberExpression(be.Right, declaringType, memberName));
}