Compiler Error CS0815
Cannot assign 'expression' to an implicitly typed local
An expression that is used as the initializer for an implicitly typed variable must have a type. Because anonymous function expressions, method group expressions, and the null literal expression do not have a type, they are not appropriate initializers. An implicitly typed variable cannot be initialized with a null value in its declaration, although it can later be assigned a value of null.
With C# version 10 Lambda expressions and method groups with natural types can be used as initializers in var
declarations.
To correct this error
- Provide an explicit type for the variable.
- Or specify natural types with C# version 10 and higher.
Example
The following code generates CS0815:
// cs0815.cs
class Test
{
public static int Main()
{
var d = s => -1; // CS0815
var e = (string s) => 0; // CS0815 for C# versions before 10
var p = null; // CS0815
var del = delegate(string a) { return -1; }; // CS0815
return -1;
}
}
See also
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