- Source:
- String.Searching.cs
- Source:
- String.Searching.cs
- Source:
- String.Searching.cs
Returns a value indicating whether a specified substring occurs within this string.
public: bool Contains(System::String ^ value);public bool Contains (string value);member this.Contains : string -> boolPublic Function Contains (value As String) As BooleanParameters
- value
- String
The string to seek.
Returns
Boolean
true if the value parameter occurs within this string, or if value is the empty string (""); otherwise, false.
Exceptions
ArgumentNullException
value is null.
Examples
The following example determines whether the string "fox" is a substring of a familiar quotation. If "fox" is found in the string, it also displays its starting position.
using namespace System;int main(){ String^ s1 = "The quick brown fox jumps over the lazy dog"; String^ s2 = "fox"; bool b = s1->Contains( s2 ); Console::WriteLine( "Is the string, s2, in the string, s1?: {0}", b ); if (b) { int index = s1->IndexOf(s2); if (index >= 0) Console::WriteLine("'{0} begins at character position {1}", s2, index + 1); }}// This example displays the following output:// 'fox' is in the string 'The quick brown fox jumps over the lazy dog': True// 'fox begins at character position 17string s1 = "The quick brown fox jumps over the lazy dog";string s2 = "fox";bool b = s1.Contains(s2);Console.WriteLine("'{0}' is in the string '{1}': {2}", s2, s1, b);if (b) { int index = s1.IndexOf(s2); if (index >= 0) Console.WriteLine("'{0} begins at character position {1}", s2, index + 1);}// This example displays the following output:// 'fox' is in the string 'The quick brown fox jumps over the lazy dog': True// 'fox begins at character position 17let s1 = "The quick brown fox jumps over the lazy dog"let s2 = "fox"let b = s1.Contains s2printfn $"'{s2}' is in the string '{s1}': {b}"if b then let index = s1.IndexOf s2 if index >= 0 then printfn $"'{s2} begins at character position {index + 1}"// This example displays the following output:// 'fox' is in the string 'The quick brown fox jumps over the lazy dog': True// 'fox begins at character position 17Class Example Public Shared Sub Main() Dim s1 As String = "The quick brown fox jumps over the lazy dog" Dim s2 As String = "fox" Dim b As Boolean = s1.Contains(s2) Console.WriteLine("'{0}' is in the string '{1}': {2}", s2, s1, b) If b Then Dim index As Integer = s1.IndexOf(s2) If index >= 0 Then Console.WriteLine("'{0} begins at character position {1}", s2, index + 1) End If End If End SubEnd Class'' This example displays the following output:' 'fox' is in the string 'The quick brown fox jumps over the lazy dog': True' 'fox begins at character position 17Remarks
This method performs an ordinal (case-sensitive and culture-insensitive) comparison. The search begins at the first character position of this string and continues through the last character position.
To perform a culture-sensitive or ordinal case-insensitive comparison:
On .NET Core 2.1 and later versions: Call the Contains(String, StringComparison) overload instead.
On .NET Framework: Create a custom method. The following example illustrates one such approach. It defines a String extension method that includes a StringComparison parameter and indicates whether a string contains a substring when using the specified form of string comparison.
using System;public static class StringExtensions{ public static bool Contains(this String str, String substring, StringComparison comp) { if (substring == null) throw new ArgumentNullException("substring", "substring cannot be null."); else if (! Enum.IsDefined(typeof(StringComparison), comp)) throw new ArgumentException("comp is not a member of StringComparison", "comp"); return str.IndexOf(substring, comp) >= 0; }}open Systemopen System.Runtime.CompilerServices[<Extension>]type StringExtensions = [<Extension>] static member Contains(str: string, substring, comp: StringComparison) = if substring = null then invalidArg "substring" "substring cannot be null" if Enum.IsDefined(typeof<StringComparison>, comp) |> not then invalidArg "comp" "comp is not a member of StringComparison" str.IndexOf(substring, comp) >= 0String s = "This is a string.";String sub1 = "this";Console.WriteLine("Does '{0}' contain '{1}'?", s, sub1);StringComparison comp = StringComparison.Ordinal;Console.WriteLine(" {0:G}: {1}", comp, s.Contains(sub1, comp));comp = StringComparison.OrdinalIgnoreCase;Console.WriteLine(" {0:G}: {1}", comp, s.Contains(sub1, comp));// The example displays the following output:// Does 'This is a string.' contain 'this'?// Ordinal: False// OrdinalIgnoreCase: Truelet s = "This is a string."let sub1 = "this"printfn $"Does '{s}' contain '{sub1}'?"let comp = StringComparison.Ordinalprintfn $" {comp:G}: {s.Contains(sub1, comp)}"let comp2 = StringComparison.OrdinalIgnoreCaseprintfn $" {comp2:G}: {s.Contains(sub1, comp2)}"// The example displays the following output:// Does 'This is a string.' contain 'this'?// Ordinal: False// OrdinalIgnoreCase: TrueImports System.Runtime.CompilerServicesModule StringExtensions <Extension()> Public Function Contains(str As String, substring As String, comp As StringComparison) As Boolean If substring Is Nothing Then Throw New ArgumentNullException("substring", "substring cannot be null.") Else If Not [Enum].IsDefined(GetType(StringComparison), comp) Throw New ArgumentException("comp is not a member of StringComparison", "comp") End If Return str.IndexOf(substring, comp) >= 0 End FunctionEnd ModulePublic Module Example Public Sub Main Dim s As String = "This is a string." Dim sub1 As String = "this" Console.WriteLine("Does '{0}' contain '{1}'?", s, sub1) Dim comp As StringComparison = StringComparison.Ordinal Console.WriteLine(" {0:G}: {1}", comp, s.Contains(sub1, comp)) comp = StringComparison.OrdinalIgnoreCase Console.WriteLine(" {0:G}: {1}", comp, s.Contains(sub1, comp)) End SubEnd Module' The example displays the following output:' Does 'This is a string.' contain 'this'?' Ordinal: False' OrdinalIgnoreCase: TrueIf you are interested in the position of the substring value in the current instance, you can call the IndexOf method to get the starting position of its first occurrence, or you can call the LastIndexOf method to get the starting position of its last occurrence. The example includes a call to the IndexOf(String) method if a substring is found in a string instance.
See also
- IndexOf(Char)
- LastIndexOf(String)
