如果您需要异常的Number或Message属性的测试用例，您可以使用构建器（使用反射），如下所示：

using System;
using System.Data.SqlClient;  // .NetCore using Microsoft.Data.SqlClient;
using System.Linq;
using System.Reflection;

public class SqlExceptionBuilder
{
    private int errorNumber;
    private string errorMessage;

    public SqlException Build()
    {
        SqlError error = this.CreateError();
        SqlErrorCollection errorCollection = this.CreateErrorCollection(error);
        SqlException exception = this.CreateException(errorCollection);

        return exception;
    }

    public SqlExceptionBuilder WithErrorNumber(int number)
    {
        this.errorNumber = number;
        return this;
    }

    public SqlExceptionBuilder WithErrorMessage(string message)
    {
        this.errorMessage = message;
        return this;
    }

    private SqlError CreateError()
    {
        // Create instance via reflection...
        var ctors = typeof(SqlError).GetConstructors(BindingFlags.NonPublic | BindingFlags.Instance);
        var firstSqlErrorCtor = ctors.FirstOrDefault(
            ctor =>
            ctor.GetParameters().Count() == 7); // .NetCore should be 8 not 7
        SqlError error = firstSqlErrorCtor.Invoke(
            new object[] 
            { 
                this.errorNumber, 
                new byte(), 
                new byte(), 
                string.Empty, 
                string.Empty, 
                string.Empty, 
                new int() 
            //,new Exception()  // for .NetCore 
            }) as SqlError;

        return error;
    }
 
    private SqlErrorCollection CreateErrorCollection(SqlError error)
    {
        // Create instance via reflection...
        var sqlErrorCollectionCtor = typeof(SqlErrorCollection).GetConstructors(BindingFlags.NonPublic | BindingFlags.Instance)[0];
        SqlErrorCollection errorCollection = sqlErrorCollectionCtor.Invoke(new object[] { }) as SqlErrorCollection;

        // Add error...
        typeof(SqlErrorCollection).GetMethod("Add", BindingFlags.NonPublic | BindingFlags.Instance).Invoke(errorCollection, new object[] { error });

        return errorCollection;
    }

    private SqlException CreateException(SqlErrorCollection errorCollection)
    {
        // Create instance via reflection...
        var ctor = typeof(SqlException).GetConstructors(BindingFlags.NonPublic | BindingFlags.Instance)[0];
        SqlException sqlException = ctor.Invoke(
            new object[] 
            { 
                // With message and error collection...
                this.errorMessage, 
                errorCollection,
                null,
                Guid.NewGuid() 
            }) as SqlException;

        return sqlException;
    }
}

然后，您可以让一个仓库模拟（例如）抛出一个如下所示的异常（这个例子使用Moq库）：

using Moq;

var sqlException = 
    new SqlExceptionBuilder().WithErrorNumber(50000)
        .WithErrorMessage("Database exception occured...")
        .Build();
var repoStub = new Mock<IRepository<Product>>(); // Or whatever...
repoStub.Setup(stub => stub.GetById(1))
    .Throws(sqlException);

这应该行得通：

using System.Runtime.Serialization;

var exception = FormatterServices.GetUninitializedObject(typeof(SqlException)) 
                as SqlException;

mockAccountDAL.Setup(m => m.CreateAccount(It.IsAny<string>(), "Display Name 2", 
                     It.IsAny<string>())).Throws(exception);

但是，使用GetUninitializedObject有以下警告：
由于对象的新示例初始化为零，并且没有运行构造函数，因此该对象可能不表示该对象视为有效的状态。
如果这导致了任何问题，您可能可以使用一些更复杂的反射魔术来创建它，但这种方式可能是最简单的（如果它有效的话）。

我刚试过这个，对我很有效：

private static void ThrowSqlException()
{
    using (var cxn = new SqlConnection("Connection Timeout=1"))
    {
        cxn.Open();
    }
}

// ...
mockAccountDAL.Setup(m => m.CreateAccount(It.IsAny<string>),
                     "Display Name 2", It.IsAny<string>()))
              .Callback(() => ThrowSqlException());

对于我来说，使用Uninitialized Object方法生成一个带有消息的SqlException是最简单的方法：

const string sqlErrorMessage = "MyCustomMessage";
var sqlException = FormatterServices.GetUninitializedObject(typeof(SqlException)) as SqlException;
var messageField = typeof(SqlException).GetField("_message", BindingFlags.NonPublic | BindingFlags.Instance);
messageField.SetValue(sqlException, sqlErrorMessage);

我在找到这个问题/答案之前写了这个。对于只想要一个特定数字的SQL异常的人可能很有用。

private static SqlException CreateSqlExceptionWithNumber(int errorNumber)
{
    var sqlErrorCollectionCtor = typeof(SqlErrorCollection).GetConstructor(
        BindingFlags.NonPublic | BindingFlags.Instance,
        null,
        CallingConventions.Any,
        new Type[0],
        null);

    var sqlErrorCollection = (SqlErrorCollection)sqlErrorCollectionCtor.Invoke(new object[0]);

    var errors = new ArrayList();

    var sqlError = (SqlError)FormatterServices.GetSafeUninitializedObject(typeof(SqlError));

    typeof(SqlError)
        .GetField("number", BindingFlags.NonPublic | BindingFlags.Instance)
        ?.SetValue(sqlError, errorNumber);

    errors.Add(sqlError);

    typeof(SqlErrorCollection)
        .GetField("errors", BindingFlags.NonPublic | BindingFlags.Instance)
        ?.SetValue(sqlErrorCollection, errors);

    var exception = (SqlException)FormatterServices.GetUninitializedObject(typeof(SqlException));

    typeof(SqlException)
        .GetField("_errors", BindingFlags.NonPublic | BindingFlags.Instance)
        ?.SetValue(exception, sqlErrorCollection);
    
    return exception;
}

返回值为0 {var ex =（SqlException）格式化服务.GetUninitializedObject（类型为（SqlExceptionMock））;返回值为0 { var ex =（SqlException）(返回值为（SqlException）; var errors =生成SqlErrorCollection（错误编号，消息）;设置私有字段值（例如，“_errors”，错误）;返回ex; }

private static SqlErrorCollection GenerateSqlErrorCollection(int errorNumber, string message)
    {
        var t = typeof(SqlErrorCollection);
        var col = (SqlErrorCollection)FormatterServices.GetUninitializedObject(t);
        SetPrivateFieldValue(col, "_errors", new List<object>());
        var sqlError = GenerateSqlError(errorNumber, message);
        var method = t.GetMethod(
          "Add",
          BindingFlags.NonPublic | BindingFlags.Instance);
        method.Invoke(col, new object[] { sqlError });
        return col;
    }

    private static SqlError GenerateSqlError(int errorNumber, string message)
    {
        var sqlError = (SqlError)FormatterServices.GetUninitializedObject(typeof(SqlError));

        SetPrivateFieldValue(sqlError, "_number", errorNumber);
        if (!string.IsNullOrEmpty(message)) SetPrivateFieldValue(sqlError, "_message", message);
        return sqlError;
    }

    private static void SetPrivateFieldValue(object obj, string field, object val)
    {
        var member = obj.GetType().GetField(
          field,
          System.Reflection.BindingFlags.NonPublic | System.Reflection.BindingFlags.Instance
          );
        member?.SetValue(obj, val);
    }
}