string array.Contains?

问题:

.NET 2

string[] myStrings = GetMyStrings();    
string test = "testValue";

How can I verify if myStrings contains test?

回答1:

In .NET 2.0, you could do the following if you want the index:

int index = Array.FindIndex(
    myStrings,
    delegate(string s) { return s.Equals(test); }
);

index will be -1 if myStrings does not contain test.

If you merely want to check for existence:

bool exists = Array.Exists(
    myStrings,
    delegate(string s) { return s.Equals(test); }
);

回答2:

I have found an elegant answer at the page here http://www.dotnettoad.com/index.php?/archives/10-Array.Contains.html. What you have to do in .NET 2.0 is to cast to IList and call Contains method.

(IList<string> mystrings).Contains(test);

回答3:

Here's a .NET 2.0 compliant approach. Using Array.Find will return null if the value isn't found.

C# Approach

string[] myStrings = { "A", "B", "testValue" };
string test = "testValue";
string result = Array.Find(myStrings, delegate(string s) { return s == test; });
Console.WriteLine("Result: " + result);

If you need a case insensitive match use s.Equals(test, StringComparison.InvariantCultureIgnoreCase).

EDIT: with VB.NET 2.0 more effort is required since it doesn't support anonymous delegates. Instead you would need to add a Function and use AddressOf to point to it. You would need to set the testValue as a member or property since it will not be passed in to the predicate method. In the following example I use Array.Exists.

VB.NET Approach

' field or property ' 
Dim test As String = "testValue"

Sub Main
    Dim myStrings As String() = { "A", "B", "testValue" }       
    Dim result As Boolean = Array.Exists(myStrings, AddressOf ContainsValue)
    Console.WriteLine(result)
End Sub

' Predicate method '
Private Function ContainsValue(s As String) As Boolean
    Return s = test
End Function

回答4:

Instead of using a static array, you could use a List:

List<string> myStrings = new List<string>(GetMyStrings());
if(myStrings.Contains("testValue"))
{
    // Do Work
}

回答5:

Thought I would add another to the mix, first available in .NET 3.5, I believe:

Enumerable.Contains(myStrings.ToArray(), test)

回答6:

bool ContainsString(string[] arr, string testval)
{
    if ( arr == null )
        return false;
    for ( int i = arr.Length-1; i >= 0; i-- )
        if ( arr[i] == testval )
            return true;
    return false;
}

And this will have the best performance ever. :P

回答7:

Here is almost the exact same question on msdn. Find String in String Array As others have said you really have two options: 1) Use a list for easier checking 2) Loop through your array to find the string

回答8:

you can use Array.BinarySearch as described below.

 string[] strArray = GetStringArray();
        string strToSearch ="test";
        Array.BinarySearch(strArray, strToSearch);

回答9:

How about this:

Sub Main
    Dim myStrings(4) As String
    myStrings(0) = "String 1"
    myStrings(1) = "String 2"
    myStrings(2) = "testValue"
    myStrings(3) = "String 3"
    myStrings(4) = "String 4"

    Dim test As String = "testValue"

    Dim isFound As Boolean = Array.IndexOf(myStrings, test) >= 0

    If isFound Then
        Console.WriteLine("Found it!")
    End If
End Sub

This should work for .Net 2.0 and VB.Net.

回答10:

I assume you want to check if any elements in your array contains a certain value (test). If so you want to construct a simple loop. In fact I think you should click here.