Error CS0121 The call is ambiguous between the following methods or properties

Compiler Error CS0121 The call is ambiguous between the following methods or properties: 'TestMethod' and 'TestMethod'

The compiler was not able to call one form of an overloaded method. In other word Compiler can not decide which overload method should use.

C# Code

public class Parent
{
    public double Add(int i, double d)
    {
        return (double)i + d;
    }

    public double Add(double d, int i)
    {
        return d + (double)i;
    }
}

Call above function from Main function

static void Main(string[] args)
{
    Parent p1 = new Parent();
    double result1 = p1.Add(1, 2.2); // result1 = 3.2
    double result2 = p1.Add(1.1, 2); // result1 = 3.1
    double result3 = p1.Add(1, 2);   // Get Compiler Error CS0121
    Console.ReadKey();
}

Related Post

Why function overloading is not based on return type?

Why function overloading is not based on return type?

Compiler Error CS0121 The call is ambiguous between the following methods or properties: 'TestMethod' and 'TestMethod'

The compiler was not able to call one form of an overloaded method. In other word Compiler can not decide which overload method should use.

C# Code

public class Parent
{
    public void TestMethod()
    {
        Console.WriteLine("Message from Parent.TestMethod().");
    }

    public string TestMethod()
    {
        Console.WriteLine("Message from Parent.TestMethod() return type string.");
        return string.Empty;
    }
}

Observation

Here, will get 2 error for above C# sample code

Solution

You can resolve above error in the following ways:

• Specify the method parameters in such a way that implicit conversion does not take place.
• Remove all overloads for the method.
• Cast to proper type before calling method.