计算列表示形式（表格）

计算列是在表中创建新列并且获取的值存储于该表中的 DAX 表达式。 每次处理表时，都会对计算列表达式进行计算。

计算列表示形式

AMO 中的计算列

在使用 AMO 管理表格模型表时，对于 AMO 中的计算列没有一对一的对象匹配。 计算列由 Dimension 中的属性以及 MeasureGroup 中的属性表示。

下面的代码段演示如何向现有表格模型添加计算列。 代码中假定您具有 AMO 数据库对象 newDatabase 和 AMO 多维数据集对象 modelCube。

  
private void addCalculatedColumn(  
                   AMO.Database newDatabase  
                 , AMO.Cube modelCube  
                 , String ccTableName  
                 , String ccName  
                 , String newCalculatedColumnExpression  
             )  
{  
    if (string.IsNullOrEmpty(ccName) || string.IsNullOrWhiteSpace(ccName))  
    {  
        MessageBox.Show(String.Format("Calculated Column name is not defined."), "AMO to Tabular message", MessageBoxButtons.OK, MessageBoxIcon.Error);  
        return;  
    }  
    if (string.IsNullOrEmpty(newCalculatedColumnExpression) || string.IsNullOrWhiteSpace(newCalculatedColumnExpression))  
    {  
        MessageBox.Show(String.Format("Calculated Column expression is not defined."), "AMO to Tabular message", MessageBoxButtons.OK, MessageBoxIcon.Error);  
        return;  
    }  
  
    if (newDatabase.Dimensions[ccTableName].Attributes.Contains(ccName))  
    {  
        MessageBox.Show(String.Format("Calculated Column name already defined."), "AMO to Tabular message", MessageBoxButtons.OK, MessageBoxIcon.Error);  
        return;  
    }  
    //Add CC attribute to the Dimension  
    AMO.Dimension dim = newDatabase.Dimensions[ccTableName];  
    AMO.DimensionAttribute currentAttribute = dim.Attributes.Add(ccName, ccName);  
    currentAttribute.Usage = AMO.AttributeUsage.Regular;  
    currentAttribute.KeyUniquenessGuarantee = false;  
  
    currentAttribute.KeyColumns.Add(new AMO.DataItem(ccTableName, ccName, OleDbType.Empty));  
    currentAttribute.KeyColumns[0].Source = new AMO.ExpressionBinding(newCalculatedColumnExpression);  
    currentAttribute.KeyColumns[0].NullProcessing = AMO.NullProcessing.Preserve;  
    currentAttribute.NameColumn = new AMO.DataItem(ccTableName, ccName, System.Data.OleDb.OleDbType.WChar);  
    currentAttribute.NameColumn.Source = new AMO.ExpressionBinding(newCalculatedColumnExpression);  
    currentAttribute.NameColumn.NullProcessing = AMO.NullProcessing.ZeroOrBlank;  
  
    currentAttribute.OrderBy = AMO.OrderBy.Key;  
    AMO.AttributeRelationship currentAttributeRelationship = dim.Attributes["RowNumber"].AttributeRelationships.Add(currentAttribute.ID);  
    currentAttributeRelationship.Cardinality = AMO.Cardinality.Many;  
    currentAttributeRelationship.OverrideBehavior = AMO.OverrideBehavior.None;  
  
    //Add CC as attribute to the MG  
    AMO.MeasureGroup mg = modelCube.MeasureGroups[ccTableName];  
    AMO.DegenerateMeasureGroupDimension currentMGDim = (AMO.DegenerateMeasureGroupDimension)mg.Dimensions[ccTableName];  
    AMO.MeasureGroupAttribute mga = new AMO.MeasureGroupAttribute(ccName);  
  
    mga.KeyColumns.Add(new AMO.DataItem(ccTableName, ccName, OleDbType.Empty));  
    mga.KeyColumns[0].Source = new AMO.ExpressionBinding(newCalculatedColumnExpression);  
  
    currentMGDim.Attributes.Add(mga);  
  
    try  
    {  
        //Update Dimension, CubeDimension and MG in server  
        newDatabase.Update(AMO.UpdateOptions.ExpandFull, AMO.UpdateMode.UpdateOrCreate);  
    }  
    catch (AMO.OperationException amoOpXp)  
    {  
        MessageBox.Show(String.Format("Calculated Column expression contains syntax errors, or references undefined or missspelled elements.\nError message: {0}", amoOpXp.Message), "AMO to Tabular message", MessageBoxButtons.OK, MessageBoxIcon.Warning);  
        return;  
    }  
    catch (AMO.AmoException amoXp)  
    {  
        MessageBox.Show(String.Format("AMO exception accessing the server.\nError message: {0}", amoXp.Message), "AMO to Tabular message", MessageBoxButtons.OK, MessageBoxIcon.Warning);  
        return;  
    }  
    catch (Exception)  
    {  
        throw;  
    }  
}