List(T).IndexOf Method (T)
Searches for the specified object and returns the zero-based index of the first occurrence within the entire List(T).
Assembly: mscorlib (in mscorlib.dll)
Return ValueType: System.Int32
The zero-based index of the first occurrence of item within the entire List(T), if found; otherwise, –1.
The List(T) is searched forward starting at the first element and ending at the last element.
This method determines equality using the default equality comparer EqualityComparer(T).Default for T, the type of values in the list.
This method performs a linear search; therefore, this method is an O(n) operation, where n is Count.
The following example demonstrates all three overloads of the IndexOf method. A List(T) of strings is created, with one entry that appears twice, at index location 0 and index location 5. The method overload searches the list from the beginning, and finds the first occurrence of the string. The IndexOf(T, Int32) method overload is used to search the list beginning with index location 3 and continuing to the end of the list, and finds the second occurrence of the string. Finally, the IndexOf(T, Int32, Int32) method overload is used to search a range of two entries, beginning at index location two; it returns –1 because there are no instances of the search string in that range.