C# EF Core-字符串或二进制数据将被截断

当您有80个（+/-）列可供选择时，如何确定哪一列是罪魁祸首？使用.Net核心（netcoreapp2.2）和EF核心2.2.4

提取了一些现有代码，尝试跟踪失败的列。但是，它不起作用。我在这里和其他地方查看了几十个示例，但在EF Core 2.x中没有找到这样做的方法

public int GetColumnMaxLength(string table, EntityEntry entityEntry)
{
    // Just a rough to get the right data - always returns 0 for the moment...
    int result = 0;
    var modelContext = entityEntry.Context;
    var entityType = modelContext.Model.FindEntityType(table); // THIS IS ALWAYS NULL!

    if (entityType != null)
    {
        // Table info 
        var tableName = entityType.Relational().TableName;
        var tableSchema = entityType.Relational().Schema;

        // Column info 
        foreach (var property in entityType.GetProperties())
        {
            var columnName = property.Relational().ColumnName;
            var columnType = property.Relational().ColumnType;
            var isFixedLength = property.Relational().IsFixedLength;
        };
    }
    return result;
}

上面的代码是由try/catch的这个catch部分围绕db.SaveAsync（）调用的；声明

catch (Exception ex)
{
    // -----------------------------------------
    // no idea what this was really trying to 
    // do as it barfs out all columns...
    // -----------------------------------------

    var dataInfo = new DataInfo();

    var strLargeValues = new List<Tuple<int, string, string, string>>();

    foreach (var entityEntry in _db.ChangeTracker.Entries().Where(et => et.State != EntityState.Unchanged))
    {
        // -----------------------------------------
        // try to get the column info for all 
        // columns on this table...
        // -----------------------------------------
        dataInfo.GetColumnMaxLength("Subscription", entityEntry);

        foreach (var entry in entityEntry.CurrentValues.Properties)
        {
            var value = entry.PropertyInfo.GetValue(entityEntry.Entity);
            if (value is string s)
            {
                strLargeValues.Add(Tuple.Create(s.Length, s, entry.Name, entityEntry.Entity.GetType().Name));
            }
        }
    }

    var l = strLargeValues.OrderByDescending(v => v.Item1).ToArray();

    foreach (var x in l.Take(100))
    {
        Trace.WriteLine(x.Item4 + " - " + x.Item3 + " - " + x.Item1 + ": " + x.Item2);
    }

    throw;
}

---

如注释中所述，您需要全名，并且可以从元数据中读取全名

public int GetColumnMaxLength(EntityEntry entityEntry)
{
    int result = 0;

    var table = entityEntry.Metadata.Model.FindEntityType(entityEntry.Metadata.ClrType);

    // Column info 
    foreach (var property in table.GetProperties())
    {
        var maxLength = property.GetMaxLength();

        // For sql info, e.g. ColumnType = nvarchar(255):
        var sqlInfo = property.SqlServer();
    };
    return result;
}

---

在.NET Core 3.1和EFCore 5.0.2上，此日志记录工作时不需要其他扩展方法：

try
{
    await context.SaveChangesAsync();
}
catch(Exception ex)
{
    foreach (var entityEntry in context.ChangeTracker.Entries().Where(et => et.State != EntityState.Unchanged))
    {
        foreach (var entry in entityEntry.CurrentValues.Properties)
        { 
            var prop = entityEntry.Property(entry.Name).Metadata;
            var value = entry.PropertyInfo?.GetValue(entityEntry.Entity);
            var valueLength = value?.ToString()?.Length;
            var typemapping = prop.GetTypeMapping();
            var typeSize = ((Microsoft.EntityFrameworkCore.Storage.RelationalTypeMapping) typemapping).Size;
            if (typeSize.HasValue && valueLength > typeSize.Value)
            {
                Log.Error( $"Truncation will occur: {entityEntry.Metadata.GetTableName()}.{prop.GetColumnName()} {prop.GetColumnType()} :: {entry.Name}({valueLength}) = {value}");
            }
        }
    }
    throw ex;
}

---

使用普通SQL语句不可行吗？您使用的是哪个版本的SQL Server？2019（自CTP2起）包括消息中的表名和列名。它还应该在2017年和2016年后端口到SP2，需要跟踪标志460才能启用。如果您正在运行其中一个版本，希望您可以进行更新并启用该标志。

FindEntityType

需要完整的类型名称，或者类型本身，

typeof（订阅）

。您可以从这里开始-当具有

EntityEntry

时，不需要查找实体类型，因为它是由

元数据

属性提供的，例如

var entityType=EntityEntry.Metadata您是否尝试过将上述内容更新到v3.1？我想尝试上面的方法，但找不到缺少的DEF<代码>GetDatabaseDefinition（）

。这让我接近了！我会尽量记住发布我用这个信息创建的扩展方法。谢谢

try
{
    await context.SaveChangesAsync();
}
catch(Exception ex)
{
    foreach (var entityEntry in context.ChangeTracker.Entries().Where(et => et.State != EntityState.Unchanged))
    {
        foreach (var entry in entityEntry.CurrentValues.Properties)
        { 
            var prop = entityEntry.Property(entry.Name).Metadata;
            var value = entry.PropertyInfo?.GetValue(entityEntry.Entity);
            var valueLength = value?.ToString()?.Length;
            var typemapping = prop.GetTypeMapping();
            var typeSize = ((Microsoft.EntityFrameworkCore.Storage.RelationalTypeMapping) typemapping).Size;
            if (typeSize.HasValue && valueLength > typeSize.Value)
            {
                Log.Error( $"Truncation will occur: {entityEntry.Metadata.GetTableName()}.{prop.GetColumnName()} {prop.GetColumnType()} :: {entry.Name}({valueLength}) = {value}");
            }
        }
    }
    throw ex;
}