/// <summary>
/// Binds a 'substring' function to create a LINQ <see cref="Expression"/>.
/// </summary>
/// <param name="node">The query node to bind.</param>
/// <param name="context">The query binder context.</param>
/// <returns>The LINQ <see cref="Expression"/> created.</returns>
protected virtual Expression BindSubstring(SingleValueFunctionCallNode node, QueryBinderContext context)
{
CheckArgumentNull(node, context, "substring");
Expression[] arguments = BindArguments(node.Parameters, context);
if (arguments[0].Type != typeof(string))
{
throw new ODataException(Error.Format(SRResources.FunctionNotSupportedOnEnum, node.Name));
}
ODataQuerySettings querySettings = context.QuerySettings;
Expression functionCall;
if (arguments.Length == 2)
{
Contract.Assert(ExpressionBinderHelper.IsInteger(arguments[1].Type));
// When null propagation is allowed, we use a safe version of String.Substring(int).
// But for providers that would not recognize custom expressions like this, we map
// directly to String.Substring(int)
if (context.QuerySettings.HandleNullPropagation == HandleNullPropagationOption.True)
{
// Safe function is static and takes string "this" as first argument
functionCall = ExpressionBinderHelper.MakeFunctionCall(ClrCanonicalFunctions.SubstringStartNoThrow, querySettings, arguments);
}
else
{
functionCall = ExpressionBinderHelper.MakeFunctionCall(ClrCanonicalFunctions.SubstringStart, querySettings, arguments);
}
}
else
{
// arguments.Length == 3 implies String.Substring(int, int)
Contract.Assert(arguments.Length == 3 && ExpressionBinderHelper.IsInteger(arguments[1].Type) && ExpressionBinderHelper.IsInteger(arguments[2].Type));
// When null propagation is allowed, we use a safe version of String.Substring(int, int).
// But for providers that would not recognize custom expressions like this, we map
// directly to String.Substring(int, int)
if (querySettings.HandleNullPropagation == HandleNullPropagationOption.True)
{
// Safe function is static and takes string "this" as first argument
functionCall = ExpressionBinderHelper.MakeFunctionCall(ClrCanonicalFunctions.SubstringStartAndLengthNoThrow, querySettings, arguments);
}
else
{
functionCall = ExpressionBinderHelper.MakeFunctionCall(ClrCanonicalFunctions.SubstringStartAndLength, querySettings, arguments);
}
}
return(functionCall);
}
