如何为T []，T [] []编写重载的泛型扩展方法而没有歧义？

Question

I want to write extension methods for converting a vector and matrix into string. I did this in the following way.

For Vector

public static string GetString<T>(this T[] SourceMatrix, string ColumnDelimiter = " ")
{
    try
    {
        string result = "";
        for (int i = 0; i < SourceMatrix.GetLength(0); i++)
            result += SourceMatrix[i] + ColumnDelimiter;
        return result;
    }
    catch (Exception ee) { return null; }
}

For Matrix

public static string GetString<T>(this T[][] SourceMatrix, string ColumnDelimiter = " ", string RowDelimiter = "\n")
{
    try
    {
        string result = "";
        for (int i = 0; i < SourceMatrix.GetLength(0); i++)
        {
            for (int j = 0; j < SourceMatrix[i].GetLength(0); j++)
                result += SourceMatrix[i][j] + "" + ColumnDelimiter;
            result += "" + RowDelimiter;
        }
        return result;
    }
    catch (Exception ee) { return null; }
}

Now i am using following code which causes ambiguity.

List<double[]> Patterns= GetPatterns(); 
Patterns.ToArray().GetString();

Error

Error   5   The call is ambiguous between the following methods or properties: 
'MatrixMathLib.MatrixMath.GetString<double[]>(double[][], string)' and 
'MatrixMathLib.MatrixMath.GetString<double>(double[][], string, string)'    

Can anyone suggest me to write these extension methods correctly.

Thanks in advance.

Answer 1

您可以省略默认值，也可以在函数调用中声明T的类型

Answer 2

There is nothing wrong with your methods. It is the compiler that can't choose between them.

As you can see in the error message, the compiler could assume T to be double[] and match the first method, or double and match the second one. This will be solved by explicitly mentioning which method you want to use:

Patterns.ToArray().GetString<double>();

Answer 3

The compiler can't tell whether you want to call GetString<double[]> or GetString<double> because both methods fit the invocation.

The easiest way to solve that is to simply change one of the names (ie GetArrayString<T> ). A better solution IMO is to have only 1 method that solves both cases like this one:

public static string Join<T>(this T[] sourceMatrix, string columnDelimiter = " ", string rowDelimiter = "\n")
{
    if (sourceMatrix.Length == 0)
    {
        return string.Empty;
    }

    if (sourceMatrix[0] as Array == null)
    {
        return string.Join(columnDelimiter, sourceMatrix);
    }

    var rows = new List<string>();
    foreach (T item in sourceMatrix)
    {
        var array = item as Array;
        var row = "";
        for (int j = 0; j < array.GetLength(0); j++)
            row += array.GetValue(j) + columnDelimiter;
        rows.Add(row);
    }

    return string.Join(rowDelimiter, rows);
}

Usage:

int[] a = {1, 2, 3};
int[] b = { 1, 2, 4 };
int[][] c = {a, b};

Console.WriteLine(a.Join());
Console.WriteLine();
Console.WriteLine(c.Join());

Output:

1 2 3

1 2 3
1 2 4

---

Note: This only solves for 1-2 dimensions, but can easily be generalized to n dimensions.