C# 表达式返回 TSQL 包含关键字

Question

我有以下代码:

public Expression FilterString(string property, string Value, ParameterExpression parameter)
{
    var getname = Expression.Property(parameter, property);

    var toLower = Expression.Call(getname, "ToLower", null, null);

    var contains = Expression.Call(toLower, "Contains", null, new[] { Expression.Constant(Value.ToString().ToLower()) });

    //This will result in "LOWER(Body) LIKE '%abc123% " but I need "CONTAINS(Body, 'abc123')"

    return contains;
}

var parameter = Expression.Parameter(typeof(Message), "message");
var expressionFilter = myclass.FilterString("Body","abc123", parameter);
var lambda = Expression.Lambda(expressionFilter, parameter);

//Apply lambda to EF query object
query = query.Where((Expression<Func<Message, bool>>)lambda);

这会生成 TSQL LIKE 语句，但我希望它执行 CONTAINS 语句。

无论如何我可以修改上面的 FilterString 方法来让它这样做吗？

Answer 1

看起来您不能使用普通 EF，至少根据此处的来源:http://entityframework.codeplex.com/SourceControl/latest#src/EntityFramework/Core/Common/EntitySql/AST/BuiltInKind.cs

您必须将 Contains 添加到 AST 并生成它。 Here's a basic tutorial on DBProviders.