如何修复动态对象的InvalidCastException？

发布于 2024-11-28 05:51:01 字数 706 浏览 1 评论 0原文

ScriptEngine rubyEngine;
//...
dynamic execution_result = rubyEngine.Execute(script, scope);

if (execution_result != null && !silent)
    WriteResponce(execution_result.ToString());

此代码生成 InvalidCastException：

无法将“SOMELIB.Graphics”类型的对象转换为类型 'SOMELIB.Object'。

当比较发生时：

执行结果！= null

如果删除此比较，则execution_result.ToString() 会引发相同的异常。

我找到了解决方法：

if (execution_result is SOMELIB.Graphics)
{
    SOMELIB.Graphics g = execution_result as SOMELIB.Graphics;
    WriteResponce(g.ToString());
    return;
}

但我不明白为什么会出现此异常以及如何修复它。

原文

ScriptEngine rubyEngine;
//...
dynamic execution_result = rubyEngine.Execute(script, scope);

if (execution_result != null && !silent)
    WriteResponce(execution_result.ToString());

This code generates InvalidCastException:

Unable to cast object of type 'SOMELIB.Graphics' to type
'SOMELIB.Object'.

When the comparison occurs:

execution_result != null

If this comparison is removed, then execution_result.ToString() throws the same exception.

I have found a workaround:

if (execution_result is SOMELIB.Graphics)
{
    SOMELIB.Graphics g = execution_result as SOMELIB.Graphics;
    WriteResponce(g.ToString());
    return;
}

but I don't understand why does this exception appear and how to fix it.

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那支青花 2024-12-05 05:51:01

将动态转换为对象以避免 DLR（动态语言运行时）尝试将 ToString 方法绑定到其（真正的）动态类类型。

ScriptEngine rubyEngine;
//...
dynamic execution_result = rubyEngine.Execute(script, scope);

object result = execution_result as object;
if (result != null && !silent)
    WriteResponce(result.ToString());

Cast the dynamic to object to avoid the DLR (dynamic language runtime) try bind the ToString method to its (real) dynamic class type.

ScriptEngine rubyEngine;
//...
dynamic execution_result = rubyEngine.Execute(script, scope);

object result = execution_result as object;
if (result != null && !silent)
    WriteResponce(result.ToString());

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