C# lambda expression unable to manage a certain string compare

I have a specific lambda what doesn't seem to want to work properly although the logic seems sound.

index = llCodeList.Find开发者_如何学JAVAIndex(f => string.Compare(f.Threshold.ToString(), searchText, true ) >= 0);

f.Threshold is an integer value, it seems that the conversion doesn't happen and it breaks my search function. Can anyone shed some light on this?

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Why not ditch the string compare and explicitly check?

index = llCodeList.FindIndex(
            f => f.Threshold.ToString()
                            .Contains(searchText));

Are you sure that the search text is a subset of the threshold number?

Also it may be that you're not understanding how string.Compare works, it won't check numerical value but string value. For the above if searchText is 4 and the threshold is -40 would match your predicate. My example more explicitly demonstrates the behavior of string.Compare(...,...,...) >= 0

If you're trying to find results based on having a greater than or equal to match on threshold and searchText you could do this

int search = 0;
int32.TryParse(searchText, out search);
index = llCodeList.FindIndex(f => f.Threshold >= search);

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If my comment correctly got the gist of what you are trying to do then do something like this:

int index = -1;
int intVal;
if (int.TryParse(seachText, intVal)){
  index = llCodeList.FindIndex(f => f.Threshold >= intVal);
}

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I think you meant to check IndexOf instead of using Compare.

index = llCodeList.FindIndex(
    f => f.Threshold.ToString().IndexOf(
        searchText, StringComparison.InvariantCultureIgnoreCase) >= 0);

But the name FindIndex sounds like you'd want to return the actual index. My crystal ball says you're looking for something like

index = llCodeList.FindIndex(
    f => f.Threshold.ToString().IndexOf(
        searchText, StringComparison.InvariantCultureIgnoreCase));